Setting POSTMASTER_EMAIL not fully implemented

[mibuthu]

The optional setting POSTMASTER_EMAIL not always used.
In some places (e.g. for creating the first user) the postmaster email address is hardcoded as "postmaster@${FIRST_MAIL_DOMAIN}".
Is this intended? For me it would make more sense to always use the POSTMASTER_EMAIL setting, when it is set.

[iredmail]

It's intended.

• POSTMASTER_EMAIL is used as mail server admin's email address.
• First user is postmaster@<first-domain>, it doesn't need to be same as the one defined in POSTMASTER_EMAIL. For example, you can personal Gmail address as server admin, but you won't create gmail.com locally.