We installed a new firewall a couple days ago. The next day we started getting reports of some emails not being delivered. Most mail goes through, but to certain domains it doesn't. Those emails are piling up in Exchange 2007 as delayed. We tried telneting to the servers of these other domains and they say our domain's reputation isn't good enough or something like that.
To me it sounded like a blacklist issue. We are only on one. Could be the problem, might not be. Trying to get that figured out.
Other things i'm looking at - is there some kind of dns record that bigger companies are requiring to send them email? I forget what it's called. Soap record or something. It is to prove that your mail server really belongs to you, and isn't being spoofed. Could that cause this? What is it called and how do I implement it?
The new firewall is another possibility, but I don't see how. Anti-virus and all security settings are turned off. And we can email most domains fine.
Any advice would be helpful. The one blacklist we were on said we were on it because we emailed a spamtrap. Exchange server shows no signs it is being used to spam. The blacklist also wanted us to pay like $150 for an express whitelist. Sounds kind of sketchy.
thanks for any help.