Best AI email assistant 2026: 9 tools compared on price and what they do

There are two kinds of AI email assistant: a new mail client you move into, and a layer that works inside the Gmail or Outlook you already have. Both will draft a reply. The differences are in which mailboxes they support, whether they chase a thread for you, where your mail is processed, and what a seat costs. Here is an even-handed comparison, checked on 15 October 2026, and a way to choose.

What an AI email assistant actually does

Four jobs, in descending order of how much time they save: drafting replies from the thread, sorting mail that needs no decision out of the way, carrying follow-ups on a schedule, and summarising long threads. Most products do the first and the last. Fewer do triage well. Only a handful carry a follow-up sequence rather than reminding you to write one.

The map of what to hand over and what to keep is in what an AI email assistant can and cannot do; this post is about which product does which.

Prices below are the vendor's list price in US dollars per user per month, annual billing where it is offered, as published on each vendor's own site on the date checked. They change often; treat them as a ranking, not a quote.

The comparison table (checked 15 October 2026)

Standalone AI mail clients: Superhuman and Shortwave

Superhuman Mail is the fastest client in the group and the one with the most mature follow-up handling. Remind Me defaults to "if no reply", so a thread returns to the top of the inbox only if nobody answered; Auto Reminders set the wait; and on the Business plan Auto Drafts writes the follow-up in your voice when the reminder resurfaces. You still press send.

Split Inbox sorts incoming mail into streams. Superhuman supports Gmail and, since its Outlook launch, Microsoft 365. Starter is $25 per member per month and Business $33, both billed annually; the older monthly prices were $30 and $40.

Shortwave is Gmail-only in practice, built for Google accounts, and leans harder on the assistant: Ghostwriter learns your writing, the AI assistant searches and summarises across threads, and AI-powered filters sort mail. There is a free tier; paid plans are $30 per seat for Business, $45 for Premier and $120 for Max, with the tiers differing in model quality and daily AI usage. Shortwave names Claude models for its intelligence tiers, so processing is through Anthropic's API on Shortwave's side.

Superhuman versus Shortwave comes down to the mailbox and the follow-up. Outlook users have one choice. Gmail users who chase threads for a living will miss "if no reply" reminders in Shortwave; Gmail users who mostly search and summarise will find Shortwave's assistant deeper.

Layers on the inbox you already have: Fyxer, Inbox Zero, SaneBox and Lindy

Fyxer keeps Gmail or Outlook as the client and works behind it: it sorts the inbox into labels, drafts replies in your tone for the threads that need one, and takes notes in meetings, with a drafted follow-up email after each meeting on Pro and above. A seat covers both a Gmail and an Outlook account. Pro is $49 monthly or $37 billed annually; Team is $99; there is a free tier with a credit allowance. It does not run a multi-step chase on an unanswered thread.

Inbox Zero is the open-source option. It drafts replies in your voice, applies rules you write in plain English, blocks cold email, bulk-unsubscribes, and its Reply Zero tracker lists what you still owe and what is waiting on others. It signs in with Google and Microsoft accounts, and you can self-host it with Docker so your mail never leaves your infrastructure.

Inbox Zero's Starter is $20 monthly or $18 annual, Plus $35 or $28, Professional $50 or $42. It is the most common Fyxer alternative for anyone who wants to read the code.

SaneBox is not an AI drafter at all; it is a filtering service that works with any IMAP mailbox. SaneLater takes the low-priority mail out of the inbox, and SaneNoReplies collects the emails you sent that got no answer, which is the simplest follow-up tracker on this list. Plans are named Snack, Lunch and Dinner, differing in how many accounts and features you get, and start around $7 a month.

Lindy is an agent builder rather than an email product: you assemble an assistant that triages, drafts and follows up through its Gmail integration and others. It is the most flexible and the most work. Pricing is by credits, from $29.99 a month for 3,000, with Pro at $100 and Max at $200; a credit is about a cent of work.

Built into the mailbox: Gemini in Gmail and Copilot in Outlook

Gemini in Gmail has been included in Google Workspace Business plans since 15 January 2025, when Google folded the add-on into the subscription. Help me write, suggested replies and an AI overview of long threads are on Business Starter, Standard and Plus; Starter is $7 per user per month on an annual plan or $8.40 on flexible billing. Gemini drafts and summarises; it does not chase a thread or run a sequence, and it works only in Gmail.

Copilot in Outlook comes two ways. Copilot Chat, at no additional cost on eligible Microsoft 365 plans, includes Copilot in Outlook. The full Microsoft 365 Copilot add-on is $30 per user per month on an annual subscription and reaches into Teams, Word, Excel and PowerPoint as well. In Outlook it summarises a thread into key points with action items and suggested replies, and drafts with a "Sound like me" option that matches your style.

Copilot runs no follow-up sequences. It is the obvious first step for a Microsoft 365 organisation that already pays for the suite, and the baseline any Outlook add-on has to beat.

Where does the processing happen?

Every tool on this list reads your mail somewhere. The honest difference is where, and whose key.

• Vendor cloud, vendor's model. Superhuman, Shortwave, Fyxer, SaneBox and Lindy process on their servers; Shortwave names Claude, the others name their providers in their privacy pages. You trust the vendor's data handling.
• Platform cloud. Gemini stays inside Google's infrastructure and Copilot inside Microsoft's, under the same data terms as the rest of the suite. For a regulated organisation that already accepted those terms, this is the shortest path.
• Your infrastructure. Inbox Zero can be self-hosted, so the mail does not leave your servers; the model calls still go to whichever provider you configure.
• Your key, per request. PeakLook sends your own Anthropic, OpenAI or Gemini key with each request and never stores it, so the model provider relationship is yours and the vendor holds no key.

For Microsoft 365 accounts, also read the Graph scopes at the consent screen: Mail.Read and Mail.Send are reasonable for a drafter; full delegation is not.

How to choose

1. Start from the mailbox. Gmail: Shortwave, Superhuman, Fyxer, Inbox Zero or Gemini. Microsoft 365: Superhuman, Fyxer, Inbox Zero, Copilot or PeakLook. Anything else: SaneBox.
2. Decide whether you want a new client. Superhuman and Shortwave are faster but you move house. The layers keep your client and your shortcuts.
3. Ask whether you chase threads. If your week is sending asks and waiting, you need "if no reply" reminders at minimum and a sequence that sends on day 3, 7 and 14 ideally. Only Superhuman's reminders and PeakLook's sequences treat the follow-up as the product; the structure they automate is in how to write a follow-up email.
4. Check where the mail goes. Self-hosting, platform cloud, or your own key, in that order of control.
5. Price it per year, per seat. A $30 seat is $360 a year. Ask whether it saves an hour a week; if it does, it pays for itself many times over, and if it only summarises, it probably does not.

Whichever you choose, the tool does not replace the habit. An assistant makes each inbox session short; the inbox zero method is what makes the sessions scheduled. The same buying logic, for a different kind of assistant, is in what to look for in an AI fitness coach app.

PeakLook, in private beta

PeakLook is last on the list because it is not yet generally available: it is in private beta for Microsoft 365 and Outlook accounts, with Gmail on the roadmap and no public price. It is a layer, not a client: an Outlook add-in pane on the desktop and standalone iPhone, Android, Apple Watch, Wear OS and desktop apps. The AI drafter scans the Focused inbox, skips newsletters and saves a Reply-All draft threaded into every conversation that needs one.

Sequences are the distinguishing feature: templates with steps at +3, +7 and +14 days, each follow-up written in your voice from the original thread, sent from the server on a daily schedule with no window open, and halted the instant a reply lands. A send lock and two ledgers mean a step cannot go out twice.

Everything the machine wrote or will send is shown in gold, and your model key is sent per request and never stored. If that is the shape you want and you are on Microsoft 365, the waitlist is open; if you need Gmail today, pick from the table above.

Hen Eytan · Founder, UPeak

Builds the UPeak apps and writes up the research behind them.