The instructions and screenshots in this setup guide are for Mac OS X 10.11 (El Capitan). Previous versions of OS X are very similar, but may require more details to be entered manually. If you are using an older version of Mac OS X, you can find the information you might be asked for on our server names and ports page.
Open Mail.app. If you do not already have any accounts set up, it will prompt you to set up a new account. Otherwise, go to Mail → Preferences and select the Accounts tab. Click the + at the lower left of the screen. Select Add Other Mail Account…
Fill in your name, email address and password:
Click the Create button. The account will be created and Mail.app will start syncing your mail.
If account creation fails and you are using a custom domain, you may need to explicitly set the mail servers:
Ensure the servers set to using password authentication, and use your FastMail email address and app password to authenticate against the servers.
Still not working? Check the troubleshooting guide.
To use a different email address to your FastMail username:
Use the Aliases pop up menu to access your alternate addresses.
Use the Edit Aliases option to add, delete or change your list of alternate addresses.
In MacOS prior to 10.11 (El Capitan), there is no aliases option. Instead, in the Email Address field, replace your FastMail username with the address you wish to use instead. You can also enter multiple email addresses, separated by a comma. If you do this, Mail.app will let you choose which one you would like to use each time you compose a message.
Warning: The new Notes features are available to OS X 10.11/iOS 9 users only if you are using Apple's upgraded Notes with iCloud support. These extra features are not available if you are using IMAP based Notes through FastMail. If you don't need the new features, then we recommend you do not upgrade Notes support: once upgraded, you can't go back. Once a note goes onto iCloud, FastMail will no longer be able to synchronise with it.
If you don't already have Mail configured, you will need to add a new Notes account:
Open the System Preferences app, and go to Internet Accounts, select + to add a new account.
Select to Add Other Account.
Select Mail account.
Add in your username, your full email address and password.
Ensure Notes is selected as an account type.
View your Notes!
If your Notes do not display, check the advanced server settings.
If you do already have Mail configured, you just need to add Notes support to that account.
If you change your Mac Mail password after adding your FastMail account to Mail.app, you will need to update the settings in two places.
Click the drop-down menu next to Outgoing Mail Server (SMTP) and select the Edit SMTP Server List… option.
If you have more than one account set up, make sure you have the correct account selected at the top.
Click the Advanced tab, then focus the Password field, delete the current contents and type in your new password.
Click OK to close the SMTP dialog, then close the preferences window, saving your changes if prompted.
You should now be able to both send and receive mail again with your FastMail account. If you can do one, but not the other, try following the steps again carefully: your password may have been updated correctly for incoming mail, but not for outgoing mail, or vice versa.