Mail Block - Periodic Authentication unsuccessful.

[wshull]

Everyone,

Just recently, starting around June 14, 2025, some of the users on my Qlik SaaS have been experiencing this error when trying to use the Mail block in their Automations:

"error": "SMTP Error: Could not authenticate.",
  "serverError": "SMTP ERROR: Password command failed: 535 5.7.139 Authentication unsuccessful, the request did not meet the criteria to be authenticated successfully. Contact your administrator.

The hard part about this is that it is very periodic.  Sometimes it works, sometimes it doesn't.  Has anyone else noticed this behavior as of late.  I would understand if it failed all the time on having a wrong password, but that doesn't seem to be the case.  We have tried remaking their Mail connection, that doesn't seem to fix the problem.

Thanks for any advice.  

[Shai_E]

Hi @wshull 

If nothing is changed on the SMTP server credential wise or a settings, and the error is frequent, then perhaps a support case is in order?

Best Regards

[wshull · Accepted solution]

It turns out that the IP address that Qlik was using to try to sign in for email was found to be banned at some point in time for security reasons.  The best we can come up with was that multiple IP addresses are being used to log into email and it would fail when the one that was banned was being used.