March 26, 2016
In an effort to tighten up its anti-spam policies BT has caused problems for its broadband customers who don’t use an @btinternet.com address.
A routine security upgrade has led to customers using a desktop SMTP program, such as Outlook or Thunderbird, with their own domain name, receiving an error message when they try to send mail.
SMTP error 553 is raised when a remote server rejects the mail because the sender’s domain is not on its approved list.
BT announced the change on a help site – http://help.btinternet.com/yahoo/help/servicestatus/ – but it seems that many customers were still not aware that they needed to validate their domain.
BT has advised customers experiencing problems to visit this page – http://help.yahoo.com/l/us/yahoo/mail/original/manage/sendfrom-07.html