efa-project.org

We haven't made any changes to our EFA install (great package btw!) and one of our vendors has started to receive delivery failure messages when sending us email:

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Diagnostic information for administrators:
Generating server: mail.vendor.tld
to.me@ourdomain.tld
#< #4.0.0 X-Spam-&-Virus-Firewall; host mail.ourdomain.tld[our-ip-address] said: 450 4.7.25 Client host rejected: cannot find your hostname, [vendor-ip-address] (in reply to RCPT TO command)> #SMTP#
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Two weeks ago we were able to receive email from them just fine, however now all emails sent to us from them are failing. They've made no changes as well (so they say).

Can I force EFA to accept all email from the vendor domain and/or IP address?

googling that smtp error code leads me to this
http://www.techieshelp.com/450-4-7-1-cl ... -hostname/

short answer, the receiving mail server is doing a reverse ip lookup and is either not finding a match or it is finding a mismatch.

while i understand why people do that, i known many mail servers do not have the ability to set a correct reverse ip entry.

so, if you can, get a reverse ip lookup set on your mailserver ip and make sure the mailserver uses that name in the smtp banner.

this should resolve those errors.

(i recently had to drop one of my outgoing ips from mail sending because i could not get the provider to set the reverse mapping for me and i ended up getting too many rejections from dumb mail servers)

Hi pdwalker!

Thanks for taking the time to respond. I figured it was a reverse IP issue on their end, but they (the vendor) still maintain they've done no changes to their network that would cause their emails to be rejected. Until they figure it out, I saw that there is a way to disable client host checks in postfix universally, which I am hesitant to do. I'm still digging through documentation that would tell postfix "any email from vendor IP address/hostname will be accepted and not rejected".

Thanks again!