Why are two copies of the same email being received?
There are two mailboxes:
email@example.com has enabled Switch on mail forwarding directive to
firstname.lastname@example.org mailbox in Plesk > Subscriptions > example.com > Mail > Email Addresses > email@example.com > Forwarding and enabled Forward to directive in Plesk > Subscriptions > example.com > Mail > Email Addresses > firstname.lastname@example.org > Auto-Reply to the same
As a result, in an email is being sent to
email@example.com mailbox, the forwarding rusendsend this email to
After this, an auto-reply directive is executed and the auto-reply message is sent to
However, after this, due to enabled Forward to directive in the Auto-Reply tab, the initial email is also sent to the mentioned in this directive mailbox. That is why the
firstname.lastname@example.org mailbox receives two copies of the same email.