IMAP

Server imap.fastmail.com
Port 993
SSL/TLS Encryption Enabled, but not STARTTLS
Username Your full email address
Password Your app-specific password
Root folder/IMAP path prefix (leave blank)
Folder separator / (forward slash)

Do not enable secure password authentication (SPA). It is not needed when you use SSL/TLS encryption and it will not work.

POP

Server pop.fastmail.com
Port 995
SSL/TLS Encryption Enabled, but not STARTTLS
Username Your full email address
Password Your app-specific password

 

SMTP

Server smtp.fastmail.com
Port 465
SSL/TLS Encryption Enabled, but not STARTTLS
Authentication PLAIN
Username Your full email address
Password Your app-specific password

If your client supports STARTTLS only, you can use port 587 with STARTTLS enabled.

 

 

You may opt to use the email service app instead of your own.
You can download this app here:

Google Play            App Store