@mentions set user's email as FROM instead of Reply-to

When making an @mention, the email sent from Confluence inserts the user's email address into the From header. Some mail systems (e.g. Exchange) may reject the email if it is sent through a relay server first due user spoofing.

The Share feature will set the username as the reply to, but still use the configured email account in the Confluence Mail Server settings in the From header. @mentions should work the same way to prevent any sendmail issues and for consistency.