Like other email service providers AOL also uses SMTP protocol for sending users to the recipients. Now SMTP server may be disturbed due to incorrect settings for email clients. Clearly, it will create issues for sending and receiving emails. You need to fix the issue to resume the AOL service. Contact at AOL tech support and get fixed. Expert advice with the professional approach of the solution. An easy approach to the settings and alter the correct changes will surely be fixing your issues.