The short answer
Three things narrow this down fast. Which email provider do you use? How much do you want the assistant to do without asking? Do you want a new app, or a layer on the one you have? On Gmail only? Then Shortwave and Gmail's own Gemini features are built for you. On Outlook, or both, check provider support first. It knocks out more options than any feature will. And if you want an assistant that prepares the work and then stops for your approval, that's the line Otto draws.
Otto is ours. This list isn't paid placement and has no affiliate links. We read each product's own pages on 9 October 2026 and didn't run a head-to-head test, so every entry links to its source. Plans and features change.
How we compared them
We asked six questions, roughly in the order they decide a choice. What can it change without asking? Drafts only, or can it also send mail and archive or delete it? Which providers does it support? What does it read and keep, whole message bodies or only headers? What's the cost shape: a free plan, a trial, a per-seat price, usage credits? Which platforms does it run on? And what job is it doing: a new mail app, a layer on yours, or an assistant?
If we couldn't find a claim on the product's own pages, we left it out. A price appears only where the vendor's page states it in US dollars.
The eight
Otto
Gmail and Outlook in one app, with a calendar and tasks alongside an assistant that drafts replies, finds mail, books meetings and files things away. It asks for your approval before it sends, books or edits anything, and automatic replies only run inside limits you set. Free covers one connected account. Plus is $6.99 a month and Pro is $19.99 a month. It runs on the web and on iPhone.
It's for people on Gmail or Outlook, or both, who want mail with a calendar and tasks alongside it. There's no native Mac or Windows app, and no meeting recording. The alternatives pages say more.
Superhuman Mail
A shortcut-first client that says it's built for teams that use Gmail or Outlook. Its Mail page lists Split Inbox, follow-up reminders, Send Later, snippets, read statuses and shared views. It describes AI that drafts and, if you want, sends for you. As of October 2026 its plans page lists Mail on the Business and Enterprise plans.
Good if your day lives in the inbox and you want speed. We didn't find a free Mail plan on the page we read. See Superhuman alternatives.
Shortwave
An AI mail client for Gmail. It has AI search and AI filters, bundles, delivery schedules and a free plan. Its docs say Microsoft 365 and Exchange accounts aren't supported at this time. Apps cover Mac and Windows, plus iOS and Android.
A good fit for Gmail and Google Workspace users who want AI inside the inbox. Outlook is out. See Shortwave alternatives.
Spark
Its Free plan lists a Smart Inbox and a calendar, with unlimited accounts. The AI features and team tools are on paid plans, and the pricing page marks Autopilot and Auto-Drafts as coming soon. Same four platforms as Shortwave.
Pick it if you've got lots of accounts and want a good free client. The AI is the paid part. See Spark alternatives.
Fyxer
Works inside Gmail and Outlook. It drafts replies in your tone, and it labels mail. It also records meetings for notes. Its pricing page says it drafts and you decide what's sent, and it describes monthly credits.
Best for a week that's mostly email and meetings. Usage is credit-based, and it's an add-on rather than a mail app. See Fyxer alternatives.
SaneBox
Works with every email client. It filters unimportant mail and has BlackHole for unwanted senders, a Daily Digest, follow-up reminders and snooze. It says it looks at the sender, the subject and the date, and doesn't store full emails or attachments.
If you're happy in your current client and just want it quieter, this fits. It sorts mail but doesn't write replies. See SaneBox alternatives.
Gmail with Gemini
Google's own AI inside Gmail, including thread summaries and Help me write. Which features you get depends on your plan and on your language and region. Google keeps the current list on its Gemini in Gmail help page.
No new app to learn, which is the appeal. It's Gmail only, and eligibility varies.
Outlook with Copilot
According to Microsoft's FAQ, Copilot in Outlook can prioritize your inbox, summarize a thread, draft with Copilot and coach on tone. Some features need a Copilot license.
It's aimed at Microsoft 365 organizations, and what you get depends on the license and the client.
What they cost
Otto Free costs nothing. The rest are the lowest paid plans, in USD on monthly billing, from each vendor's own pricing page.
| Product | Lowest paid plan | Price | Notes |
|---|---|---|---|
| Otto | Plus | from $6.99/month | Pro $19.99/month; $55.99/year for Plus |
| Fyxer | Pro | from $49/month | per seat, $37/month billed yearly |
| Shortwave | Business | from $30/month | per seat |
| Spark | Plus | from $10/month | per seat, $8.25/month billed yearly |
| SaneBox | Snack | from $3.49/month | filtering for your current mail app, $2.42/month billed yearly |
Superhuman's price depends on your region, and Gmail with Gemini and Outlook with Copilot depend on your plan or license, so we've listed no figure for them. Yearly billing is cheaper where a vendor offers it.
Which to pick
- On Gmail only and want AI in the inbox? Shortwave, or Gmail with Gemini if not adding an app is the point.
- On Outlook or Microsoft 365: Outlook with Copilot if you're licensed. Otherwise Otto, Superhuman or Spark, but not Shortwave.
- On both Gmail and Outlook: one of Otto, Superhuman or Spark.
- A free client for many accounts: Spark.
- You like your client and want it calmer: SaneBox, or the filters and rules Gmail and Outlook already have.
- Meetings eat your week: Fyxer.
- You want to approve everything it does before it happens: Otto.
Whatever you pick, run one real week through it first. The side-by-side comparisons can narrow the field, and a trial does the rest.
First published on the Otto Mail blog.
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