SMTP Communication Problem

Posted on 2010-03-25
Medium Priority
Last Modified: 2012-05-09
I recently setup an exchanger server for a customer. We were getting returned e-mail for about a day due to a reverse DNS lookup problem That has been resolved but there are a couple of mail servers the keep returning our e-mail. the most common reson is below. When i google it I get so many variation that it is hard do decipher.

There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
            <mail.xxxx.org #5.5.0 smtp;554 Transaction Failed Spam Message not queued.>
Question by:CADRE308
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LVL 27

Expert Comment

ID: 28590748
Check you are not blacklisted.

mxtoolbox.com --> blacklists

LVL 27

Expert Comment

ID: 28590827
Type IP into the blacklist search.

Note that your reverse DNS will take a period of time to be seen by all recipient servers depending on how long the record is cached by receiving servers.


Author Comment

ID: 28591242
On mxtoolbox.com blacklist all is ok but SPAMRBL was timed out. I am new to exchange so what you are telling me is that the problem most likely resides with the recepiants mail server not mine???
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LVL 27

Expert Comment

ID: 28591474
If that is clean and your rDNS is ok and matches the FQDN then you should be fine, it may take day or two for the cached records to expire.

Check the following:

The reverse DNS (rDNS \ PTR) record is configured by the people who issued your IP address in most instances (so your ISP).
Below are two articles which explain the general requirements for reverse dns (rDNS\PTR) records for your IP address.
I try to adhere to the following when setting up a rDNS (PTR) record:
Be a Fully Qualified Domain Name (FQDN) such as server.domain.com (not just 'domain.com' or 'server').
Should not contain 'in-addr-arpa' and should not include words like pool or dyn etc.
Should match what you use in your SMTP HELO\EHLO hostname if possible.
For neatness and as a good rule of thumb, if your incoming mail is delivered to the same server that you use for Outgoing you should make sure all the following FQDN's match:
MX record
rDNS (PTR) record
SMTP EHLO hostname
http://www.amset.info/exchange/dnsconfig.asp (Courtesy of EE member Mestha)

Also take a look at my recent blog entry regarding setting up proper DNS data:



Author Comment

ID: 28592127
The rDNS and FQDN are all good. This has been going on all week. I went live with the mail server Monday. Most of my mail is being delivered just fine with the exception of a couple suche as bellsouth.net. any e-mail sent to a bellsouth.net account is returned.
LVL 27

Accepted Solution

shauncroucher earned 2000 total points
ID: 28595040
As long as rDNS and SMTP FQDN match and you are not on any blacklist then you can either wait and see if the situation changes or contact those domains blocking you and find out why.

You have done all you can for your domain in terms of meeting internet standards.


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