550 “REJECTED – Bad HELO – Host impersonating If you found this error for any  particular domain say linuxsurgeon.org, then first check the mx record for this domain. If the MX record is pointing to a different server, then just remove the domain entry linuxsurgeon.org from the /etc/localdomains, And add the same entry in /etc/remotedomains. [...]

On shared hosting servers you probably find your mail server’s ip blocked by other mail servers because of high mail volume or one of your users doing spamming. To change your exim IP for outgoing mail, you can edit your /etc/exim.conf file:— You can change the interface IP address for exim mail server in the [...]