There are several StartOS services that are capable of sending emails, such as BTCPay Server, Ghost, Gitea, Nextcloud, Synapse, and Vaultwarden, using third party email (SMTP) servers. The guides below are for using Gmail or Amazon SES for SMTP, but you may also use another third party provider of your choice.
You should have your 2-Step Verification on. If not, please configure it first by visiting the 2-Step Verification section.
When the 2-Step Verification is active, you should be able to see the App Password at the bottom of its configuration page. Enter the 2-Step Verification section, scroll to the bottom and click the App Passwords.
Select a name for the new app password. You may call it anything, such as “SMTP.” Click the Create button.
A random 16 character password will be created and shown to you. This is your app password. Save it somewhere secure and click Done.
Now you can use this SMTP account for any service that has the capability to send an email. The table below shows all the details you may need: