We have had an ongoing problem for several months of our mail getting returned with an error message when only sending to certain Email addresses. The error reports:

There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<technicpos.com #5.5.0 smtp;553 66.163.1.245 mail rejected due to excessive spam (Spamcop, SORBS)>

We have verified with almost every Blacklist that we ARE NOT LISTED in any database under our IP address or our Domain technicpos.com.

It also only seems to occur when sending to certain email addresses with domains at aol.com, yahoo.com, *.us etc.

We are completely baffled by this and are in need of resolving this as soon as possible. We have researched all of the known blacklists with our mail servers IP address of 66.163.1.245 and searching to see if our domain technicpos.com is listed either. All searches we perform come up clean and report that the IP address and domain are not listed in any database.

Somebody Please Help!

I can find no evidence at all of your IP having ever been listed by SpamCop (SpamCop doesn't 'do' domains). Any reports would have been sent to abuse[at]radiant.net. Have you contacted them to see if they have received any? It may well be a mis-formed error message blaming SC or SORBS when (perhaps) it's an unknown recipient or full mailbox. Other than that I'm afraid I can't help.

Yes, we did check with Radiant.net and they have received nothing reporting any abuse from us. We also thought it might be an invalid error message but the recipient does receive Email from our personal mail accounts, blackberry or webmail as usual. It only seems to be an issue when sending from our work mail server. It has been driving us crazy! Thanks for your swift response though.

Thay may have added you to an internal blacklist, either with reason or accidentally. It would have to be the receiving end to address the issue.

Lots of questions, actually ...

http://www.senderbase.org/senderbase_queri...ng=66.163.1.245
Date of first message seen from this address 2008-10-18
Volume Statistics for this IP
Magnitude Vol Change vs. Last Month
Last day ...... 0.0 .. N/A
Last month .. 1.1

Was thinkng of asking if this was the correct IP Address, but the error message snippet was allegedly specfic.

ns1.directnic.com reports the following MX records for 'technicpos.com':

Preference Host Name IP Address TTL
0 mail.technicpos.com 66.163.1.245 86400

http://www.mxtoolbox.com/blacklists.aspx?IP=66.163.1.245
Checking 66.163.1.245 against 124 known blacklists...
Listed: 0 time(s)
Timeouts:6

01/13/09 15:47:25 dig technicpos.com @ 208.67.220.220
Dig technicpos.com[at]ns1.directnic.com (69.46.234.245) ...
failed, couldn't connect to nameserver
Dig technicpos.com[at]ns0.directnic.com (69.46.233.245) ...
failed, couldn't connect to nameserver
Dig technicpos.com[at]208.67.220.220 ...
Non-authoritative answer
Recursive queries supported by this server
Query for technicpos.com type=255 class=1
technicpos.com NS (Nameserver) ns0.directnic.com
technicpos.com NS (Nameserver) ns1.directnic.com
technicpos.com NS (Nameserver) ns0.directnic.com
technicpos.com NS (Nameserver) ns1.directnic.com

and on top of that .... 66.163.1.245 resolves to 66-163-1-245.ip.tor.radiant.net

rDNS looks like the most likely issue, (trying to ignore the NS problem) with really bad configuration settings on some of the receiving systems (blaming other reasons for the rejection)

It looks like grey-listing is used on a Microsoft server, version 6.0.3790.3959 .. but that's pretty much a guess at the message traffic results.

Here is another view of your DNS 'health' - http://www.intodns.com/technicpos.com - there are some matters that could do with attention but possibly the one of immediate concern:

MX Records Your MX records that were reported by your nameservers are:

0 mail.technicpos.com 66.163.1.245

then

Reverse MX A records (PTR) Your reverse (PTR) record:
245.1.163.66.in-addr.arpa -> 66-163-1-245.ip.tor.radiant.net

While the report does not make an issue of this, it is possible that some receiving systems are seeing this as a mismatch and cause for rejection (and maybe some blocklists like SORBS might take notice and exception to it when they come across it). Combine that with a misconfigured non-delivery report and that might explain the rejections seen. Also you have no 'backup' MX which is a risk but beside the point.

Short-term, you could request whitelisting at the problem site(s) - seems you might have only instanced one. But that leaves the possibility of similar problems with other (new) contact sites.

I'm guessing that 245.1.163.66.in-addr.arpa -> mail.technicpos.com would make it all go away. But IANAT