SymptomsSmarterMail is used as mail server in Plesk. Mailbox email@example.com is configured to forward mail to firstname.lastname@example.org, email@example.com has enabled autoresponder.
When mail is sent to firstname.lastname@example.org directly, autoresponder works correctly.
When mail is sent to email@example.com and redirected to firstname.lastname@example.org, autoresponder does not work.
The same configuration on Mailenable server does work correctly in both cases.
CauseThe reason of such behavior is that in SmarterMail Autoresponder works by event on SMTP service. But SmarterMail redirection does not use SMTP service when mail is redirected locally.
So Autoresponder simply does not run in this case.