Having accounts on both hotmail and AOSmell, and after having reviewed the Mailer-Daemon from my bounced emails far too many times, I can tell you almost unequivocally, the problem is almost always on the AOSmell side.
It has to do with them still believing they are the tail wagging the dog that is the Internet.
Sure was the case 10 years ago, but not anymore.
However, for many of the same reasons we still have DOS code working within Windows, and for many of the same reasons the US Missile Defense Shield is still co-ordinated using COBOL software left over from the Nixon administration, (pre-Microsoft), AOSmell still uses their aged proprietary email system. Many of the reasons have their roots of origin stemming from VHS vs. Betamax Syndrome. In the early 90's AOL wanted you to use THEIR stuff, and ONLY their stuff. That much hasn't changed.
If people were smart, they would dump AOL as fast as possible.
Or did you really think the building of AOL world headquarters in the shadow of Langley was a coincidence?
Do you really think it is coincidence that both AOL and the Langley IT building are both built directly above the physical hardware and cabling/fiber optic network that serves as one of the 7 primary hubs of the Internet? EVERYTHING that goes on the Internet, electronically moves through these seven hubs. Its a critical part of the sophisticated mechanism that makes the Internet what it is.

And in the end, its all about controlling the flow of information, stemming the flow of resistance, and dampening down the Questioning of Authority.

(sorry, forgot I wasn't in the politics forum - grin)