Solved: 550-Unrouteable address 550 Sender verify failed

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mortensencs🇺🇸

550-Unrouteable address 550 Sender verify failed

We are receiving the following error when a particular user is sending to a particular domain:

mailstore.XXXXX.net #<mailstore.XXXXXX.net #5.0.0 smtp; 550-Verification failed for <ouruser@ourdomain.com> 550-Unrouteable address 550 Sender verify failed> #SMTP#

The user can send to every other domain, except for this one in particular. Other users can send to this domain with no problems, but this user gets rejected with the above error.

We are running Exchange 2010 and earlier this week setup Postini accounts for all users on the domain. Postini is only handling inbound email.

Any ideas?

Thanks

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kain21🇺🇸

It is possible that the user having the trouble has been blacklisted by the mail server of the receiving organization. Alternatively, I have seen this issue happen with DNS problems but since other users aren't having the issue I'd have to lean to the first option.

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mortensencs🇺🇸

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mortensencs🇺🇸

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It was an issue that was not on our end, but rather another vendor.

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Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.