Hi,
We have one customer who is unable to send mails to us. If they use a different domain, with a different mailserver and public IP, mail works fine.
I cannot see any mails in the portal which are being blocked and I have whiltelisted the senders domain, although I dont think in this case that will have any effect.
The logs I have received from the sending server are:
2017-03-23 15:12:31 1cr4Pf-001dOF-78 <= xyz@domain.co.uk H=(whuk101.redbackinternet.net) [127.0.0.1]:46795 I=[127.0.0.1]:25 P=esmtpa A=dovecot_login:xyz@domain.co.uk S=631 id=7cd01d794fbf0f59926f459a82a9cc00@domain.co.uk T="test" from <xyz@domain.co.uk> for user.name@recipientdomain.co.uk
2017-03-23 15:12:33 1cr4Pf-001dOF-78 H=cluster5a.eu.messagelabs.com [216.82.251.230]: SMTP error from remote mail server after RCPT TO:<user.name@recipientdomain.co.uk>: 421 Service Temporarily Unavailable
2017-03-23 15:12:33 1cr4Pf-001dOF-78 == user.name@recipientdomain.co.uk<user.name@recipientdomain.co.uk> R=dkim_lookuphost T=dkim_remote_smtp defer (-44) H=cluster5a.eu.messagelabs.com [216.82.251.230]: SMTP error from remote mail server after RCPT TO:<user.name@recipientdomain.co.uk>: 421 Service Temporarily Unavailable
You can see 421 Service Temporarily Unavailable. No other customers are reporting this error, I have checked to see if the senders IP has been blacklisted and it doesnt look like it has (109.203.103.150).
How do we get this resolved? Any help would be appreciated. As a side note, cluster5a.eu.messagelabs.com is our secondary MX record and not primary - I find it a little strange that secondary is being used, as it has a higher weight.
Thanks,
Daniel