Fastmail has a built-in way to stay signed in to several accounts: click your avatar, add another account, and switch between them without logging out. It works in the web interface, the Fastmail desktop app and the mobile apps. Before adding accounts, check whether an alias would do, since one Fastmail account can receive mail at many addresses. If you want two Fastmail accounts open side by side rather than switching back and forth, WebCatalog Desktop can keep each one in its own window.
Aliases or a separate account?
Fastmail explains the difference in multiple email addresses vs. multiple users. An alias delivers mail to your existing inbox without a separate login, and you can add up to 600 of them under Settings > My email addresses at no extra cost. A separate user has its own login, mailbox and storage, which suits a colleague, a family member, or a business you want kept fully apart.
Switch between Fastmail accounts
Fastmail's guide to switching users describes the steps:
- Click your avatar in the upper-right corner of Fastmail.
- Select Add another account. This opens the Select user screen.
- Click Log in as another user and sign in with your second account.
To switch later, click your avatar and select the other account. Fastmail lets you stay logged in to multiple accounts at once in the web interface, the Fastmail desktop app and the mobile apps.
You can also add several Fastmail accounts to a mail client such as Apple Mail or Thunderbird, but that needs IMAP access, which Fastmail's Basic plan doesn't include, plus an app password for each client.
Open Fastmail accounts side by side with WebCatalog Desktop
Fastmail's switcher shows one account at a time. WebCatalog Desktop (macOS, Windows, and Linux) turns Fastmail into a desktop app with its own window and Dock or taskbar icon, and its profiles keep each account's cookies and session separate. That way your personal and business inboxes can sit in two windows at the same time.
- Install WebCatalog Desktop and add Fastmail from the catalog.
- Open Profiles, select Add profile, and name it, for example Personal.
- Open Fastmail with that profile and sign in with that account.
- Add another profile, such as Business, and sign in with your other Fastmail account.
The help article on creating and managing profiles has more detail. A profile can be reused across apps, so your Business profile can also hold the Slack and Notion accounts you use for that work. Grouping them in spaces keeps each context in its own window, while the profiles keep the logins apart.
Conclusion
Fastmail's avatar menu covers switching well, and aliases often remove the need for a second account. If you want several Fastmail accounts open at once in their own windows, download WebCatalog Desktop.
