DSN: to <billing@gbb.com.ng>; reason: Service unavailable; sessionid:

[firdausi12]

Hello Team,

Please i need someone to help me resolve this issue as mail is bouncing back to sender and Saved message in /var/spool/dead/dead.letter 

[Stephen_G]

Hello firdausi12,

Thank you for getting in touch with us about your email bouncing issue! I'm going to ask for a solution and reply to this thread with an update as soon as possible.

Thanks,

Stephen

[distillednetwork · Accepted solution]

According to the error: 

Verify the sending server PTR record

Important: The sending IP address must match the IP address of the hostname specified in the Pointer (PTR) record. PTR records are also called Reverse DNS records.

Your sending IP address must have a PTR record. PTR records verify that the sending hostname is associated with the sending IP address. Every IP address must map to a hostname in the PTR record.

if you are sending from the domain gbb.com.ng, but from the IP address  41.222.211.3, gmail is rejecting it because of the DNS records.  You will need to update your PTR records to reflect the domain you are trying to send from.