Outlook account not properly receiving or sending.  All settings checked for accuracy and nothing has changed. Called Microsoft support and was told it was an ISP problem. Called ISP technical support (AT&T) and told everything working properly and it was an Microsoft Outlook problem. Incoming e-mail senders receive notification "account not in service".  Outgoing e-mails are not sending although message states outgoing mail is being sent.  Pop-up window to verify account name and password is frequent but not accepted.  Passwords have not changed but are not accepted.

E-mails coming through web based account (att.yahoo.com) are not appearing in Outlook although Outlook is designated as "default". 

Any help with this two week old problem will be graciously appreciated.