cPanel users can create an Email Forwarder for an email address that does not already exist within their account. For example, if John is the administrator of a site, he may want to tell users to contact him at email@example.com so that he does not have to disclose his personal email address. Instead of creating a new email account, he can simply create a forwarder as outlined in our documentation.
Creating this forwarder allows him to receive mail addressed to firstname.lastname@example.org within his email@example.com account, without requiring the creation of an additional email account.
Occasionally when configuring a forwarder in this manner, users sending email to firstname.lastname@example.org might report that they receive a bounceback message with the following content:
LMTP error after RCPT TO:<email@example.com>: 550 5.1.1 <firstname.lastname@example.org>
User doesn't exist: email@example.com
Despite this, John will notice that the message was forwarded successfully and he received it in his inbox at firstname.lastname@example.org.
This problem occurs when email@example.com did exist in the cPanel account previously, but was removed improperly. firstname.lastname@example.org will not appear on the Email Accounts page in cPanel, but it exists in the cPanel account's mail directory:
To prevent the "550 5.1.1 User doesn't exist" bounceback message, this directory can be removed or renamed, for example:
mv -v /home/user/mail/domain.tld/admin /home/user/mail/domain.tld/admin-bak