If you are getting SMTP 550 error, you should call @ sbcglobal.net customer support phone number. According to the request for request 5321 mentioned above, the standard form of 550 SMTP status code 550 requested action mailbox was not taken unavailable has been translated as almost 550 as requested was not executed. The box is not accessible. The IETF document lists the following three options with other reasons:-

• The target address is invalid
• It is missing the rights to use the SMTP service
• The request has been rejected for policy reasons

This means that the error message will always appear in an e-mail client who wants to use SMTP for the transfer of electronic mail but the request fails for one of the other reasons listed above.

Does the SMTP server pass for the cause of the problem due to the client and depending on the type of related mail system as well as the client? As a result, error messages may appear at least partially, albeit in a different way, although it often refers to the exact same problem.