Facing issue with email send using Gmail SMTP settings. same i had used earlier it was working fine but sudden it is failing to send. giving error, unable to send error email for logged incident. please see below snap for reference.
I want to correct something for point 4.
If your Google account has Two Factor Authentication enabled (2FA), you can not enable or disable that setting.
Instead, you will need to create Application Specific Passwords and use those as your password (a common behavior with almost all the third party systems that use 2FA today, GitHub, Azure DevOps etc).
And yes, I do know that I did not change my password from 2014.
I have enabled less secure app , i have mentioned error in topic heading from application log and using mail extension 3.6 but i don't know about telnet.
1. Please go in the Logging subsystem, enable stack tracing, try to send again your mail.
After it fails, go in the ThingWorx storage folder, in logs, and check the last entry in the ErrorLog.log file (look for the exact file name corresponding to today).
That line should correspond to your error. Tell us the stack trace, exactly how it is there.
2. What was the message after running telnet?