Find an AI tool that writes useful replies—not just new emails. Compare 10 options by thread awareness, tone control, Gmail and Outlook support, and whether they draft or send responses.
Introduction
An AI email reply generator turns an incoming message into a draft you can review and send. The useful distinction is how much context it can draw on: a standalone writer may need you to paste the message, while an inbox assistant can work within the conversation. Neither should be trusted to invent facts or commitments on your behalf.
The best choice depends on where you answer email and how much control you want over the result. For a routine scheduling reply, a quick suggestion may be enough; a customer complaint may require the full thread, a carefully controlled tone, and substantial human editing. This guide ranks 10 tools by how well they support email reply drafting, including relevance, tone control, editing effort, and fit with Gmail or Outlook workflows. It also separates tools that suggest wording from those that can take further action. That distinction matters: saving a few keystrokes is different from letting software move a conversation forward, especially when a reply could promise a deadline or disclose sensitive information.
Key Findings
- Shortwave is the best starting point for thread-aware replies inside a dedicated Gmail-based inbox.
- Microsoft Copilot is the more direct choice for drafting replies within Outlook.
- Gemini for Gmail helps draft everyday replies without moving to another inbox.
- Superhuman suits people who want AI drafting alongside a faster, keyboard-driven email workflow.
- Gmelius is designed for teams managing shared Gmail conversations.
- Review AI-generated replies before sending, especially when they could contain incorrect details or commitments.
The 10 Best AI Email Reply Generators, Ranked
Shortwave is the best starting point if you want thread-aware email replies inside a dedicated inbox. Microsoft Copilot and Gemini for Gmail make more sense if you want to stay in Outlook or Gmail. The ranking weighs reply context, editing control, setup, and whether a tool drafts for review or can act on a message automatically.
1. Shortwave
Shortwave is an email app built around Gmail, with AI features inside the inbox rather than in a separate writing window. Its strongest advantage for replies is access to the conversation you are answering: you can ask it to draft a response to a thread without first copying the message elsewhere. It also lets you search and ask questions about email history, which is useful when a reply depends on a detail buried in an older conversation.
That context is the reason Shortwave leads this ranking. A reply to “Can we use the same timeline we discussed last month?” is much harder to draft well from the latest message alone. Shortwave gives you a way to find the earlier discussion before you approve the wording. You can prompt for a shorter answer, a different tone, or a particular point to include, then edit the resulting draft in the composer. The assistant helps prepare the message; you remain responsible for reviewing and sending it.
The trade-off is substantial: adopting Shortwave means using another inbox interface, not simply adding a button to Outlook. It is the clearest fit for Gmail users who handle long-running conversations and want AI drafting alongside email search. If you must work in Outlook, start with Copilot instead.
2. Microsoft Copilot
Copilot in Outlook is the natural choice for people whose email already lives in Microsoft 365. It can help draft a reply in Outlook and summarize a long conversation before you write one. That pairing matters: a summary can surface the decision, open question, or commitment you need to address, while the drafting feature turns your instructions into editable text.
Copilot works within the Outlook workflow rather than requiring a separate email client. For a reply to a project update, you might tell it to acknowledge the revised deadline, ask for the remaining dependency, and keep the response concise. You can refine the draft and make your own edits before sending. Where Outlook offers coaching on a draft, that serves a different purpose: it helps assess wording you have written rather than deciding what your answer should be.
Its main limitation is that access and capabilities depend on the Microsoft 365 environment your organization has enabled. Copilot should not be treated as an autonomous correspondent that knows every relevant fact outside the available email and work context. Check figures, commitments, and recipients yourself. It ranks below Shortwave for readers shopping for a dedicated AI inbox, but above broader writing tools because it fits directly into an established Outlook reply workflow. It is less compelling if your day-to-day inbox is Gmail.
3. Gemini for Gmail
Gemini for Gmail is the most direct route to AI-assisted replies if you already work in Gmail. In supported Gmail environments, its writing features can suggest a response to a message and help you refine the draft. That removes the copy-and-paste step involved in using a general chatbot, while keeping the final email in the familiar Gmail composer.
The distinction to watch is between generating an answer and establishing that the answer is correct. Gemini can use the email you are replying to as context, but an apparently fluent response may still miss a condition discussed elsewhere or promise something you have not approved. For a routine scheduling reply, a short prompt may be enough. For a dispute or a question about an earlier agreement, read the thread and give explicit instructions about the outcome you want. You can adjust the draft’s wording and tone, then edit it before sending.
Gemini is a good fit for individuals and teams that want help with everyday Gmail correspondence without changing inboxes. Its availability depends on the Google account and Workspace configuration in use, so confirm that the relevant Gmail features are enabled. It is not the right pick for an Outlook-centered team, and it should not be confused with a workflow tool that independently decides which incoming messages deserve an automatic response.
4. Superhuman
Superhuman combines an email client built for rapid inbox processing with AI writing features. Its appeal is not only that it can produce reply text; it puts drafting within a keyboard-driven workflow for moving through messages, composing responses, and clearing the inbox. For someone answering a high volume of individual emails, that surrounding workflow may matter more than another tone preset.
Superhuman’s AI can help draft and rewrite messages in the context of your email workflow. You can use it to turn a brief instruction into a reply, then change the language yourself before sending. That makes it particularly useful when you know what you need to say but do not want to write the first version from scratch. It is still worth reading the conversation before accepting a draft: speed is not a substitute for catching a changed date or an unanswered question.
Superhuman supports Gmail and Outlook account workflows, though adopting it means working in Superhuman’s interface rather than adding a writing assistant to your existing composer. That is the central trade-off. Pick it if you want a different way to process email and will use its navigation and drafting together. If you only need occasional AI help inside the Outlook or Gmail interface you already like, Copilot or Gemini is the more direct choice. Replies are drafts for your review, not a reason to stop checking what goes out.
5. Gmelius
Gmelius is best understood as a Gmail-based team inbox tool with AI-assisted replies, not simply a personal email writer. Its distinguishing use case is a shared address: several people may need to manage incoming requests, assign ownership, and answer consistently. In that setting, a quick draft is valuable only if the right teammate sends it with the right information.
Gmelius brings reply assistance into the team’s email workflow, alongside features for handling shared conversations. A teammate can use AI to prepare a response from the message context, adjust the wording, and review it before sending. The operational benefit is that drafting sits near the conversation and the team’s handling of it, rather than in a disconnected text generator. For a support or operations inbox, that is a more useful combination than polished prose alone.
The limitation is scope. Gmelius is centered on Gmail, so an Outlook-based shared inbox should look elsewhere. It also requires a team to decide who owns replies and which messages need human judgment; AI-generated text does not resolve conflicting assignments or authorize promises on the team’s behalf. Choose Gmelius when collaborative inbox management is as important as drafting. For a single person who wants better wording without shared-mailbox features, Gemini or a writing assistant is a simpler fit.
6. MailMaestro
MailMaestro focuses more narrowly on the act of writing and replying than the team-inbox tools above it. It provides AI drafting within email workflows, including Gmail and Outlook, so you can start from an incoming message, specify what the reply should say, and edit the proposed response. That makes it an appealing middle ground: more email-specific than a general writing assistant, without requiring you to move into a new inbox.
Its practical strength is instruction-led drafting. If a customer asks for an exception you cannot grant, you can direct the assistant to decline clearly, acknowledge the request, and offer the approved alternative. The resulting wording still needs review, especially if the original thread contains conditions that would change your answer. Tone controls and rewriting help with presentation; they cannot establish your organization’s policy or make an unsupported commitment safe to send.
MailMaestro is best for people who want an AI reply helper close to the Gmail or Outlook composer and prefer to retain control over the final message. It is less suitable if your real problem is sorting a shared queue, retrieving facts across a large email history, or triggering follow-ups in other systems. Treat it as a draft-and-edit tool rather than an automatic responder: its value is getting a usable first version into your hands, not deciding when a response should go out.
7. Lindy
Lindy belongs on this list for a different reason from the inbox-native tools: it is an AI agent and workflow builder that can be configured to handle steps around an email, including preparing responses. The distinction matters if “generate a reply” is only one part of the job. You may also need to identify a type of request, gather relevant information, and decide whether a human should approve the answer.
That flexibility comes with setup work. A useful Lindy workflow needs a clear trigger, access to the relevant mailbox, instructions about what information it may use, and a rule for what happens after it drafts. Tone can be expressed in those instructions, but a carefully worded prompt does not guarantee that an agent has found the correct answer. For an inquiry that involves a contract term or a customer-specific exception, draft-for-review is safer than allowing the workflow to send on its own.
Lindy is a better fit for repeatable, defined processes than for someone who just wants a reply button in a composer. It can be configured around connected email and work tools, but the exact mailbox and actions available depend on the connections used. Choose it when you can describe the conditions under which a response is appropriate. If each message needs nuanced human interpretation, an inbox assistant with editable drafts will be easier to supervise.
8. Grammarly
Grammarly is a broader writing assistant, not a dedicated email reply system. Its value is helping turn your intended answer into clearer language and revising text you have already written. In an email composer where Grammarly is available, you can use its writing assistance to draft or rework a response, adjust the tone, and catch wording that sounds abrupt or confusing.
That makes it useful for sensitive everyday situations: following up without sounding accusatory, declining a meeting politely, or shortening a reply that has become harder to read than the original question. Grammarly is especially effective when you supply the facts and the desired outcome yourself. It does not replace reading the thread, and its presence in a composer should not be mistaken for permission to assume it has retrieved every earlier message or attachment.
Grammarly can fit Gmail and Outlook writing workflows through its supported browser and app experiences, but how it appears depends on the environment you use. Its suggestions remain editable text; you review and send the email in your mail application. Choose it if the recurring problem is phrasing rather than finding context or orchestrating responses. If you need an assistant to answer a question from a long email history, Shortwave, Copilot, or Gemini is a more relevant starting point.
9. Proton Scribe
Proton Scribe is a writing assistant within Proton Mail. Its place in this ranking is specific: it helps compose and revise email while giving Proton Mail users a writing option in the email environment they already use. It is not a general Gmail or Outlook assistant, nor is it an autonomous tool for responding to everything that arrives.
Scribe can help produce a draft from your instructions and refine its wording. For a reply, you need to provide the essential point you want to make and check the result against the incoming message. That distinction is important for sensitive correspondence: a well-written answer can still disclose too much, omit a necessary qualification, or misstate an obligation. Review the recipient, content, and any attachments before sending. Proton Scribe helps with the writing; you decide what information belongs in the message.
The strongest reason to choose it is that you already use Proton Mail and want writing assistance without moving the task into an unrelated email workflow. Its limitation for this comparison is equally clear. Readers looking specifically for thread-aware email replies across Gmail or Outlook should choose an assistant built for those inboxes instead. Proton Scribe produces text for your review in Proton Mail; it should not be selected as a substitute for team routing or rule-based automated replies.
10. Zapier
Zapier is a workflow automation platform, not a dedicated AI email reply generator. It earns a place here because it can connect an incoming-email trigger, an AI drafting step, and an outgoing-email action. That approach is useful when the goal is to respond to a defined class of messages, not merely to get a writing suggestion while you read your inbox.
For example, a workflow could identify requests that match a narrow set of conditions, use supplied instructions to draft an acknowledgement, and route the draft for review. A more automated setup can send a response when its conditions are met. The difference between those designs is consequential: a draft gives someone a chance to catch a misclassified message, while automatic sending requires confidence in the trigger, the input data, and the allowed wording. Tone and content are controlled through the workflow’s instructions and any approved text you provide.
Zapier can work with Gmail, Outlook, and other connected apps, but you must build and maintain the workflow; it does not become a thread-aware inbox assistant by virtue of connecting to email. Choose it for repetitive, well-defined responses or for processes that also need to update another system. Do not choose it as the quickest way to answer an unpredictable personal inbox. Its low rank reflects that narrower fit, not a lack of usefulness for automation.
| Rank and tool | Reply approach | Supported inbox or input method | ||
|---|---|---|---|---|
| 1. Shortwave | AI drafting inside an email client | Gmail account in Shortwave | ||
| 2. Microsoft Copilot | Drafting and summarization in Outlook | Supported Microsoft 365 Outlook environment | ||
| 3. Gemini for Gmail | Reply suggestions and writing assistance | Supported Gmail environment | ||
| 4. Superhuman | AI writing within a fast-processing email client | Gmail or Outlook account in Superhuman | ||
| 5. Gmelius | AI-assisted replies in a team inbox | Gmail-based team workflow | ||
| 6. MailMaestro | Instruction-led email drafting | Gmail or Outlook writing workflow | ||
| 7. Lindy | Configured AI-agent workflow | Connected email and work tools | ||
| 8. Grammarly | General writing and rewriting assistance | Supported Gmail or Outlook composer experience | ||
| 9. Proton Scribe | Writing assistance in Proton Mail | Proton Mail | ||
| 10. Zapier | Triggered, multi-step automation | Connected Gmail, Outlook, or other apps |
How to Choose the Right Reply Generator
Choose an AI email reply generator by testing it against messages you actually receive. The best fit answers the sender’s question without inventing details, preserves commitments from earlier messages, sounds like you, and takes less effort to correct than writing from scratch. Check how much of the conversation it can use before judging the draft.
- Check context accuracy. Give each tool an email that refers to an earlier decision, such as “Can we use the revised deadline?” A useful reply should identify the deadline from the conversation. If it cannot, it should leave the detail for you to supply rather than guess.
- Assess tone in a real situation. Try a polite refusal or a response to an unhappy customer. Email tone control matters when a draft must be firm without sounding dismissive. Look beyond tone labels: does the wording suit your relationship with the recipient?
- Count the edits. Track corrections to facts, missing answers, awkward phrases, and unnecessary apologies. An AI email writing tool that produces polished prose but needs substantial rewriting may not improve your workflow.
- Test a long thread. Ask for a reply to a conversation with changed dates or competing requests. Long email thread summaries can help you review what matters, but verify that the draft follows the latest decision, not an outdated one.
- Check the writing surface. An inbox-based tool may reduce copying between windows; a standalone writer can work when you provide the relevant text yourself. Confirm which context the tool actually has access to rather than assuming it sees your whole inbox.
Run the same incoming email through each shortlisted tool, give each the same instructions, and compare the drafts against the original thread. Choose the one that makes the fewest consequential mistakes, not the one that writes the smoothest first sentence.
Inbox Access, Automation, and Privacy Safeguards
An inbox-connected AI assistant can use the message and conversation context it is permitted to access; a pasted-text generator sees only what you give it. Drafting is also different from sending: some tools leave every reply for your approval, while automation can send messages when configured conditions are met. Check both access and sending controls before connecting an inbox.
An AI email assistant for Gmail or Outlook typically requires you to authorize a connection or enable it within your organization’s workspace. During setup, inspect the requested permissions: reading messages, creating drafts, and sending mail are different levels of access. A pasted-text tool avoids a persistent inbox connection, but copying a message into it still shares that content with the tool. Remove confidential details before pasting.
Use this checklist before enabling automatic email replies:
- Keep human approval on for anything involving commitments, complaints, negotiations, or personal information. Check the recipient, quoted thread, attachments, and factual claims before sending.
- Limit automation to narrow triggers, such as acknowledging receipt of a message sent to a designated mailbox. Avoid broad rules that respond to every incoming email; they can misfire on spam, mailing lists, or an ongoing exchange.
- Exclude sensitive categories, including legal, medical, financial, employment, and security-related messages. Route them to a person instead.
- Check email data privacy terms: what content the provider processes, how long it retains it, whether it uses content to improve models, and whether administrators can revoke access.
- Test a sending rule with a controlled mailbox before applying it to real conversations, and establish who can pause it if replies go wrong.
A draft-only workflow is the safer default when the consequence of a mistaken reply is greater than the time saved by sending automatically.
Conclusion
The best AI email reply generator is the one that produces accurate drafts without forcing you to change how you handle mail. Shortwave is a strong starting point if you want a dedicated inbox with conversation context; Microsoft Copilot or Gemini for Gmail is a more natural fit if you intend to stay in Outlook or Gmail. A writing assistant suits hands-on drafting, while automation makes more sense for narrowly defined, repeatable responses. Before choosing an email reply assistant, try several real messages: a straightforward request, a long thread with an earlier commitment, and one where the right answer is to ask for clarification. Look for drafts that address the actual question without inventing facts or promising action you have not approved. Reliable AI email responses still need human review when a mistake could affect a customer, disclose sensitive information, or commit you to a deadline.
Frequently Asked Questions
What is the best AI email reply generator?
The best AI email reply generator depends on your inbox and how well its drafts reflect the conversation. Shortwave is a starting point for Gmail users who want to work with inbox context; Microsoft Copilot is relevant to Outlook users, and Gemini for Gmail fits Gmail workflows. Try the same messages in each candidate and compare accuracy, tone, and how much editing the drafts need.
Is there an AI that can answer my emails?
Yes, AI email assistants can draft answers to incoming messages, and some workflows can be configured to send replies under specified conditions. Drafting and sending are separate capabilities, so check which one a tool actually provides. For important conversations, review the draft against the original email before sending it or enabling an automated workflow.
Which AI email assistant works with Outlook?
Microsoft Copilot is a direct option to investigate for drafting replies in Outlook. Other assistants may connect to Outlook or help you write a response from text you copy into them, but that does not necessarily give them the same conversation context or in-inbox workflow. Check compatibility with your Outlook setup and whether you can review replies before sending.
Which AI email assistant works with Gmail?
Gemini for Gmail works within Gmail; Shortwave, Gmelius, and Superhuman offer other Gmail-centered workflows. Their reply features differ, so compare what conversation history each can use, where drafts appear, and how you approve or edit them. If you also use Outlook or another inbox, confirm support for that account separately.
Do AI reply generators understand an entire email thread?
Not always. An inbox-connected assistant may have access to earlier messages, while a standalone generator usually relies on the thread text you provide. Access does not guarantee that a draft will catch every detail, especially in a long exchange. Before sending, check that it answers the latest question and gets names, dates, and commitments right.
Is it safe to connect an AI reply assistant to my inbox?
It can be, but safety depends on the permissions you grant, how message content is handled, and what controls you can set. Check what the assistant can read, draft, and send before connecting it. For sensitive correspondence, review the provider’s data-handling terms; for consequential or automated replies, retain approval or set narrow sending conditions.