SYMPTOMS
SmarterMail is used as mail server in Plesk. Mailbox mailbox@domain1.tld is configured to forward mail to mailbox@domain2.tld, mailbox@domain2.tld has enabled autoresponder.When mail is sent to mailbox@domain2.tld directly, autoresponder works correctly.
When mail is sent to mailbox@domain1.tld and redirected to mailbox@domain2.tld, autoresponder does not work.
The same configuration on Mailenable server does work correctly in both cases.
CAUSE
The 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.