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Exchange 2003 messages sent using SMTPSVC not delivered

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  • Exchange 2003 messages sent using SMTPSVC not delivered

    So I've got an odd problem that I've not been able to find an answer to yet.

    To give a little background, my company has an in house CRM solution that our developers have created. Now Iím not familiar with how itís been built or how this was setup originally, however they use the SMTP service to connect to our Exchange server to send out bulk mail to our clients, specifically market updates to their cell phones via a text message as well as daily updates to their email addresses.

    This had been working for awhile, but recently this week it stopped working. When I say stopped working I mean we can still send email to all domains just fine from Outlook, however when sending from our CRM solution, some emails make it through, others get delayed and then others, specifically to the domain I know of for sure are not being delivered at all. We get no bounced messages from these, and exchange tracking shows them leaving our domain, and like I said some of them do actually make it through.

    Iím assuming the cause of the problem is due to the receiving mail servers believe that itís a relayed email that may be spam, however this is just an assumption. Iíve seen the headers on the two differently sent emails. From Outlook for example, it looks like a standard email header, however when sent from our CRM it says basically our web server sent the email by way of our mail server.

    I also believe that authentication is not being used to make the SMTP connection, as the connection breaks whenever I uncheck the option for anonymous access within the SMTP authentication section.

    Now we did make an addition to our internet connection when this issue started to occur. However, I believe either something we did threw a red flag and took us off existing white lists our previous administrator has gotten us on, or itís 100% coincidence. We originally had an ATT connection with a block of IP addresses as our only existing internet connection. We added a backup Comcast connection we are using to also offload non-essential things like IM and general web browsing. There are provisions that were made in our Adtran router that make sure that our mail server and web servers continue to use our ATT connection entirely, we even made a provision that all port 25 data went out that connection. No DNS entries have changed, I verified everything using NSLOOKUP and mxtoolbox and even made sure we werenít on any blacklists, and everything is green across the board, and again using Outlook works fine.

    So basically it comes down to the SMTP relayed emails arenít getting delivered for some reason I cannot come up with.

    Any ideas? I really donít feel like going in on Monday and making phone calls to various providers and requesting to put us on their white-lists. If I left anything out or you need more information please let me know.