Ok, I'm gonna go out on a big fat limb here, and explain something I've discovered about Jodo's mail servers, which MAY OR MAY NOT be the source of all our AOL delivery woes. Firstly, a quick background... I was sending out a mere 40 emails earlier today, in an ASP script that uses CDO. Note, the script uses CDO drop-mail folders, it does NOT specify an SMTP server. Therefore Windows SMTP Server of that machine is taking over the sending to Jodo's mail servers - or they send out directly, I don't know which. I suspect all mail goes through designated servers. Anyway, out of a mere 40 sendouts, we got 3 bouncebacks!. That's huge! We're sending to some BIG corporate clients, you see, and they have spam filtering up to their armpits, like AOL does. All the bounces came back with variations on the following error message: Code: Reporting-MTA: dns;abjhwin1-kgnrv5 Received-From-MTA: dns;abjhwin1-kgnrv5 Arrival-Date: Sun, 26 Feb 2006 18:00:03 -0500 Final-Recipient: rfc822;[email protected] Action: failed Status: 5.5.0 Diagnostic-Code: smtp;504 <abjhwin1-kgnrv5>: Helo command rejected: need fully-qualified hostname I looked up error 504, and it says here, among other places, that the mail was rejected because the sending server has no FQDN (qualified domain name). For some reason, that server of Jodo's has the string "abjhwin1-kgnrv5" as its "FQDN"... which is course is completely wrong. This implies that the mail servers at Jodo aren't set up properly, DNS-wise. I checked the IP address of where the mail was being sent from on Jodo's network: http://www.dnsstuff.com/tools/ptr.ch?ip=188.8.131.52 Lo and behold, no PTR records, no reverse DNS possible. Read the print at the bottom of that page: Note that all Internet accessible hosts are expected to have a reverse DNS entry (per RFC1912 2.1), and many mailservers (such as AOL) will likely block E-mail from mailservers with no reverse DNS entry. Bingo I think. I suspect this is why AOL and other anti-spam systems reject mail sent from Jodo's servers. Sooooo.... Jodo, a solution please! Can we get those servers set up properly with PTR/FQDN so we can send mail in peace? There's not much point in having "Sender ID" options set up, if a major issue like DNS is outstanding. It would probably lower the risk of you getting your mail servers blacklisted too, since they would currently be put into the "very suspicious" category of any spam monitoring systems, since they have no reverse DNS. So the big question... Am I on the right track here or talking complete bollocks?