I have a problem with sending authenticated e-mails via SMTP on my hosting with CPanel using Exim.
The problem occurs only when the script send (connection) is performed internally on the server. When I run the same script in an external environment sending will be runs smoothly.
SMTP -> get_lines(): $data is "535 Incorrect authentication data "
I believe the problem is some configuration of WHM / Exim, because until last week was working, but some settings were changed to prevent automated spam submissions.
I do not know which settings are relevant to the solution of the problem. If you need to enter any parameters of WHM setup, just tell me.
Best Answer
if I understand you right you have this error only when sending to localhost? if so, check that SMTP AUTH is enabled when connecting to lo. using telnet on the SMTP port (presumably 25) used by your script, send the initial EHLO command and check that the proper SMTP auth method used by your script is advertised.