Configuring the IMAP path prefix

An IMAP path prefix tells your mail client where to look for your mail.

Most clients will automatically set up the IMAP prefix with no issues.

When the IMAP prefix is not properly set up, you won’t receive mail at all, or your mail will appear inside an extra Inbox folder.

To troubleshoot, please check the advanced account settings in your mail client for your Fastmail account. We support connecting to us in one of two ways:


  • IMAP Path Prefix:   (leave blank) with Port: 993


  • IMAP Path Prefix: INBOX with Port: 993


  • IMAP Path Prefix:   (leave blank) with Port: 992

Whatever your mail client currently has set, try the alternative and see if that works.

Apple Mail

Apple Mail will attempt to auto-detect settings for you, which includes overriding any manual configuration settings. This is a helpful feature, but it can also cause problems with your mailbox.

To troubleshoot, please disable the "Automatically detect and maintain server settings" option for your Fastmail account in the Apple Mail client.

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