Reverse connect to MXs failed SMTP error 550

[hinarei]

I've been trying send an email out to one particular domain and keep
receiving this 550 error reply:
There was a SMTP communication problem with the recipient's email server.
Please contact your system administrator.
<#5.5.0 smtp;550 reverse connect to MXs failed>


how do I go about fixing this? it seems its only one particular person, and
I've not got them blocked on my Exchange server (as I use a third party
software for spam and other controls)

 

[Vanguard]

I've been trying send an email out to one particular domain and keep
receiving this 550 error reply:
There was a SMTP communication problem with the recipient's email server.
Please contact your system administrator.
<#5.5.0 smtp;550 reverse connect to MXs failed>


how do I go about fixing this? it seems its only one particular person,
and
I've not got them blocked on my Exchange server (as I use a third party
software for spam and other controls)

Tell your e-mail provider that their MX record is missing or screwed up in
their DNS server. The receiving mail server is checking that mails sent
from your domain come from a mail server that your domain says is a valid
mail server. This eliminates getting mails from infected user hosts that
run mail servers but obviously aren't authorize to send e-mails from that
domain. The receiving mail server connects back to the sending mail
server's DNS server to get its MX record and then compares it against the
Received header to see if your mail originated from your domain's authorized
mail servers.

So your e-mail provider isn't providing valid mail servers in MX records in
their DNS server. Or you are trying to subvert your ISP by sending mails to
some off-domain SMTP server (to abuse it). Or you are running your own mail
server which violates your ISP's terms of service since obviously they
aren't going to put you in an MX record in their DNS server.

If you are running Exchange, maybe you are also running your own
externally-facing mail server (rather than your ISP's). You'll have to add
an MX record to your DNS server, and that DNS server must be reachable from
the outside so recieving mail servers can query it for the MX record.