[FIX] ir.mail_server: be more lenient when validating From address

When a user has their email as name, the system will
construct the From header as "email<email>".
We previously forbade this, because the naive
check only counts the number of emails in
the From header.
We might need to drop that assert or implement
something better in the future.
[FIX] ir.mail_server: be more lenient when validating From address

When a user has their email as name, the system will
construct the From header as "email<email>".
We previously forbade this, because the naive
check only counts the number of emails in
the From header.
We might need to drop that assert or implement
something better in the future.