To use Delta Chat with your Fastmail email address you have to generate a specific password for it.
You can do that in the Fastmail web interface at “Settings / Account: Password & Security / Third-Party-Apps: Add”:
- Enter your Password to be able to make changes. Then click “New App Password”.
- Choose a new name for the password.
- At access, choose “Mail (IMAP/POP/SMTP)”.
- Click “Generate password”.
- Enter the 16-digit password shown there into the Delta Chat password field. Careful - leave out the spaces, it’s just 16 digits. Better copy-paste it.
Afterwards you can use Delta Chat as usual.
If your login email does not end with
@fastmail.com, you will need to manually type server information by clicking “Advanced” in Delta Chat and entering the details specified in the “Technical specs” link below.