5.5.1 501 Error, Can't Send Mail [closed]?

Typically, after connecting to an SMTP server, the first line of the request is simply: HELO It looks as if the SMTP server you're connecting to now expects the hostname as an argument: HELO example. Com Make the change and retry.

Problem is solved before your answer but Thanks very much! HostName was deleted on mail server, so problem occured. After I edited hostname, problem is solved.

Best regards – Faruk KAYA Jul 27 at 10:05 Glad you got it sorted. :) – Mikaveli Jul 27 at 10:22.