AI email apps compared: mello, Superhuman, Shortwave, Gmail, Outlook and Spark
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Most email apps now have an assistant, but they differ in two ways that matter more than any single feature. First, what they are: some are mail services, others are apps on top of a Gmail or Outlook account. Second, how the AI is turned on and what it reads. Here are six of them side by side, as of October 2026.
At a glance
What the table says about each product comes from its maker’s own pages, as of October 2026.
| What it is | Works with | AI | |
|---|---|---|---|
| mello | A mail service | Its own mailboxes; any IMAP app | On by default, and each part can be switched off: follow-ups, reply reminders, suggested to-dos, reply drafts, translation |
| Superhuman | An email app | Gmail and Outlook | Auto Drafts, Instant Reply, Ask AI |
| Shortwave | An email app | Gmail and Google Workspace | An agent, AI search, summaries, AI filters |
| Gmail with Gemini | A mail service | Gmail | Help me write, summaries, Suggested Replies; more on paid plans |
| Outlook with Copilot | A mail service and apps | Outlook.com; work accounts | Summaries, and drafts and coaching on work accounts |
| Spark | An email app | Google, Outlook, iCloud, Yahoo, Exchange, IMAP | Writing, translation, summaries; off by default |
A mail service, or an app on top
Superhuman, Shortwave and Spark are apps: your mail stays where it is, and the app connects to it. That means you keep your address, but the app’s features only exist inside the app, and you need an account somewhere else.
Gmail and Outlook are mail services with AI added by the same company. mello is a mail service too, but a small, independent one: your mail lives at mello, and you can read it in mello’s webmail or in any mail app over IMAP.
The others, one by one
- Superhuman works inside your Gmail or Outlook account. Auto Drafts writes replies from the context of your inbox, calendar and the web; Instant Reply offers quick answers; Ask AI answers questions about your email in plain language. It is built for speed, with keyboard shortcuts, Split Inbox and follow-up reminders.
- Shortwave needs a Gmail or Google Workspace account to sign in. Microsoft 365 and Exchange aren’t supported, and Outlook.com only by forwarding. Its agent can organize, schedule, write and search from a prompt, and it adds summaries at the top of each email and filters you write in plain English.
- Gmail with Gemini offers Help me write, AI Overview summaries of threads and Suggested Replies to personal accounts, some of them only in the US. Questions about your inbox, the AI Inbox and Proofread need a Google AI plan or an eligible Workspace plan.
- Outlook with Copilot: Microsoft 365 Personal and Family include Copilot in Outlook for @outlook.com, @hotmail.com, @live.com and @msn.com addresses, within usage limits; it can summarize long threads. With a work Copilot license, it also drafts, coaches you on tone and clarity, and helps schedule meetings.
- Spark connects to most providers, including any IMAP account. Its +AI features write, translate and summarize, and an AI Assistant finds and acts on mail. +AI is off until you turn it on, and is included in the paid plans.
How mello does it
mello’s assistant is meant to remember things for you rather than to write everything for you. It is on from the start, and each part has its own switch under Settings → AI:
- Follow-ups: when a message you sent gets no reply in 3 days, it suggests a nudge, already drafted.
- Reply reminders: mail waiting on your answer comes back after 7 days, with a reply drafted.
- Suggested to-dos: asked to do something, it suggests the task, with its date, for you to accept.
- Reply drafts: type
/aiand what to say in a reply, then Enter. - Translation: a message in another language gets a translate link.
- Search by meaning: finds mail by what it’s about rather than its exact words.
When a feature is on, the text it needs goes to the AI provider, Anthropic or OpenAI, under business terms that don’t allow training on it. Nothing is ever sent on your behalf. More in AI for email, without giving it everything.
When another one is the better choice
- You want to keep your Gmail or Outlook address: Superhuman, Shortwave or Spark, or simply Gemini or Copilot in the account you have.
- You want summaries and answers about your whole inbox: mello’s webmail doesn’t summarize threads or answer questions. Superhuman’s Ask AI, Shortwave’s agent and Gemini on a paid plan do. With mello, you get the same by connecting Claude or ChatGPT to your mailbox.
- You want an account today: mello is invite only for now. The others are open to everyone.
Where mello is different
- Your mail and the AI under one roof, with a switch for each part. You don’t need a second company between you and your mailbox, and turning a feature off in Settings → AI stops what it sends to the AI provider.
- It works outside the app. Follow-up reminders, snooze and send later run on the server, so they work in Apple Mail, Thunderbird or your phone’s mail app too.
- Bring your own assistant. mello’s MCP server lets Claude or ChatGPT work with your mail, calendar, tasks and contacts. It can only prepare drafts unless you tick Also allow sending mail when you connect it.
- Calendar, contacts, tasks and private addresses included, in one app.
How to switch
If you use one of the apps on top of Gmail or Outlook, moving to mello means moving the account underneath:
mello is invite only for now: request an invite.