This is not a request for help, but a brief description of what I had to do to get email notification working with Fastmail, in the hope of helping you safe some time. I’m running Truenas 25.10.1 community edition.
As a reminder, you can’t use your regular Fastmail credentials <your_email>@fastmail.com with your password to have services use your mail account. Fastmail requires you to set up a specific password for any app that you’d like to use with your email account. You do this in Fastmail Settings → Privacy&Security → Manage app passwords and access.
You need to create a specific password for your Truenas email setup. The configuration in Truenas is pretty simple, but I struggled with a few stumbling blocks. Below are the settings that worked for me:
Send method: SMTP
From email: *this doesn’t need to be your Fastmail address, I chose truenas@
Outgoing mail server: smtp_dot_fastmail_dot_com
Mail server port: 465
Security: SSL (implicit TLS)
*check the SMTP Authentication box
Username:
Password: <your app specific passord, not your regular mail account password>
What tripped me up for a while was that the email address of the truenas_admin user was different from my Fastmail email. Once I set the truenas_admin email to my Fastmail address, everything started to work. Dealing with and troubleshooting email transports is nothing new for me, but I found the error messages that I received when sending test emails rather infuriating and not helpful at all, that’s why I’m writing this up.