Over the years we have had a lot of difficulty getting email delivered to AOL email addresses - checking our delivery logs it seems that the AOL mail servers regularly become unreachable, which causes a general failure of mail delivery. Our outbound mail delivery provider automatically blocks access to addresses which are bouncing to prevent reputation problems - repeated attempts to deliver email to a bad address can lead to ISPs blocking you for suspected spamming. As such, we have set the system to automatically restrict users accounts where their email address is bouncing emails back as undeliverable to alert users to a problem and to prevent further attempts to deliver email which might cause us reputation problems. AOL seems to be the worst offender here, with regular outages that cause problems for multiple users. Because of the amount of work it causes us, we may actually be forced to prevent users from using AOL addresses at all on the forums - although we haven't yet taken that step. We strongly recommend that if you use an AOL email address, you consider changing it to a different provider to help prevent problems with your account. We generally find that Gmail addresses work well as a suggested alternative.