Delegate your day.
Email apps for Outlook, compared
Outlook is fine if your organization runs on it. If you want an assistant and a calendar and Microsoft To Do beside your mail on any Outlook account, Otto connects to the one you have.
You just approve.
The short version
- Any app below opens your existing Outlook account. Your address and your mail stay with Microsoft.
- Otto and Spark connect Outlook accounts. Shortwave doesn't support Microsoft 365 at this time, and Mimestream is built for Gmail.
- Work or school accounts may need an IT administrator to approve Otto once.
- Last reviewed 2 November 2026. Plans change, so check each page before paying.
The short answer
If your organization runs on Microsoft 365, Outlook is the app your IT team supports. Want an assistant that drafts and books, with your Outlook calendar and Microsoft To Do beside the mail? Otto connects to your Outlook or Microsoft 365 account and keeps your address. Spark and the Gmail app also open Outlook accounts. Switching apps never moves your mail, so you can try one and go back if it's not for you.
At a glance
| App | Works with | Platforms | Suits |
|---|---|---|---|
| Outlook | Outlook.com, Hotmail, work or school, and other providers | Microsoft's own app | Staying with Microsoft's app |
| Otto | Outlook, Microsoft 365 and Gmail | Web and iPhone | Mail, calendar, To Do and an assistant that asks first |
| Spark | Outlook, Exchange, Google, iCloud, Yahoo, IMAP | Mac, Windows, iOS, Android | Many accounts on a free plan |
| Gmail app | Gmail, plus Outlook, iCloud, Yahoo and IMAP | Google's own app | One app for a Gmail and an Outlook address |
| Apple Mail | iCloud, Google, Microsoft Exchange, Yahoo | iPhone and Mac | A simple app for several accounts |
What to check before you choose
Start with which Microsoft accounts the app opens. Otto connects Outlook.com and Hotmail, along with Live and Microsoft 365 accounts. Apple's guide names Microsoft Exchange but not Outlook.com, so check your account type.
Some Microsoft 365 organizations need an administrator to approve a new app first, so find out whether yours does. If it does, Otto gives you an approval link to share with them.
Ask what the assistant does when it doesn't ask you first. Otto shows a review card for ordinary sends and deletes, and for bulk changes.
Check where your calendar and tasks end up. That's easy to forget. Otto reads your Outlook calendar and syncs tasks both ways with Microsoft To Do.
And look at what it costs once the trial ends. That's where free plans differ most in what they include.
Why add Otto to Outlook
Otto sits on top of your Outlook account and isn't a new mailbox. It'll draft a reply from the thread, proposes a meeting on your Outlook calendar with a Teams link where the event is set up for one, and captures the follow-up in Microsoft To Do. Each one comes back as a card for you to approve, and sends and deletes wait for you, as do bulk changes.
Microsoft pushes new mail to Otto, so it appears as it arrives. Folders and search follow Outlook's own rules, and so do bulk actions. Those differ from Gmail's, so check the result before you retry.
What it costs
Free covers one connected account with core mail, calendar and tasks, plus an AI allowance. Paid tiers add more accounts and capacity, plus extra features. The competitor prices below come from each vendor's own pricing page, which we read in October 2026.
| Product | Lowest paid plan | Price | Notes |
|---|---|---|---|
| Otto | Plus | from $6.99/month | Pro $19.99/month; $55.99/year for Plus |
| Spark | Plus | from $10/month | per seat, $8.25/month billed yearly |
Outlook, the Gmail app and Apple Mail don't have a separate plan in this table. Microsoft's Copilot FAQ says its Copilot features need a Microsoft Copilot (work) license.
Where Otto fits, and where it doesn't
Otto fits if you're on Outlook or Microsoft 365, want a calendar and To Do beside your mail, and want to approve what an assistant does. It also fits if you read a Gmail address too.
It doesn't fit if you want a native Windows or Mac app, or iCloud or Yahoo or IMAP accounts, which it doesn't connect. And it won't give you a new address. Leaving Microsoft's mail service altogether is a provider change, and Outlook alternatives covers that.
Read more
- Outlook alternatives and the roundup of Outlook alternatives
- The AI email for Outlook guide
- Otto vs Outlook and Copilot
- Otto vs Spark and Spark vs Outlook
- How the day fits together: email with calendar and tasks
- Plans are on the pricing page
How we checked this
Last reviewed 2 November 2026. Sources: Microsoft's account guide and Copilot FAQ, Google's account guide, Apple's account guide, Spark's pricing page and home page, and Shortwave's provider guide. Otto is ours, so weigh what we say about it with that in mind. Nobody paid for a place here.
Questions, answered
Which email app works with Outlook and Microsoft 365?
Microsoft's Outlook opens Outlook accounts, and so do Otto and Spark. The Gmail app can hold an Outlook address too. Shortwave's provider guide says Microsoft 365 and Exchange are not supported at this time.
Will I lose my Outlook address or mail if I switch apps?
No. These apps open your existing Outlook account. Your address and mail stay with Microsoft, and you can go back to Outlook at any time.
Can I connect a work Microsoft 365 account to Otto?
Yes, though some organizations require an IT administrator to approve Otto once for everyone. Share the approval link from Settings, then Accounts.
Try your next step in Otto
Core mail, calendar and tasks are free. AI has an allowance.
Open Otto