550 “REJECTED – Bad HELO exim error

We have a client having his email rejected from some mail server with the following error:

SMTP error from remote mail server after MAIL FROM:<[email protected]> SIZE=1655:
host mydomain.com [xxx.xxx.xxx.xxx]: 550 "REJECTED - Bad HELO - Host impersonatin [main.mydomain.com.br]"

This error may cause for some websites those MX record pointed to different server/domain.
In this situation first check the MX record of the domain and see if it is in the same server.
If its is not then delete the entry for the particular domain from the file, /etc/localdomains
Then you need to add the same entry in /etc/remotedomains.

Once done restart the exim service.It will resolve the problem.

Another option is to find the following line in exim.conf  and  comment it.

drop
condition = ${if match{$sender_helo_name}{$primary_hostname}}
message   = "REJECTED - Bad HELO - Host impersonating [$sender_helo_name]"