Email Delivery Problems?

You should describe your scenario a little more. Get a lot of rejections? Get a lot of customer spam going into remote recipient's spam folder? Get a lot of deferrals? What types of problems specifically do you have?

I do agree that maintaining email delivery is a job of its own, if its important that all of your client's email makes it to the inbox at the recipient's end.

The biggest problems I see are with services such as Hotmail / MSN / Live, Yahoo!, and also AOL and Comcast to a lesser extent. They all seem to use various combinations of technologies -- SPF, Sender ID, DomainKeys, DKIM, rate-limiting from single IPs that send emails to many different recipients during a day, greylisting. And they often defer email for periods of time depending upon what technologies you are not using that would make your emails more favorable and your email delivery more likely and speedy.

And, it doesn't help that most of the free webmail services and certain large ISP email users are clueless idiots who falsely tag emails as spam when they are legitimate emails from friends or legitimate emails based upon them signing up on websites. Those same clueless people also like to forward their email from their other domains into their <insert large webmail operator> accounts hoping to have the large webmail operator better filter all the spam [including the spam that came into the original account that forwarded the spam], and the large webmail provider doesn't appreciate having spam forwarded so the burden is on the large webmail provider to filter it... in return they defer / reject your email / make it appear in their customer's spambox even if it isn't spam. It's a beautiful thing [note the sarcasm].

I won't go into all of the technical things you can do - I'll let somebody else suggest some things. And if you are running a cPanel server, you may have some options but not others [and that applies to all mail systems]. One thing you can do is be vigilant about your customers email practrices. Educate them about how forwarding their spam to those larger webmail providers and ISPs can and will cause their mail [and all your other customer's mail on the machine] to be looked upon less favorably if they do it.

Make sure that if your customers set up forwards to those places, that they also have a valid POP3 account with the same name as the alias that they set up so that your server's spamassassin will do some filtering. If they just set up an alias and forward it to an external address, all of the spam along with all of the legitimate mail will get forwarded to that external address.

If mail administration is your only job, it's an enjoyable experience. I love email administration. However, the vast majority of people handling email administration are either clueless or are jacks-of-all-trades and can't spend every work moment putting out email fires.

M