SMTP problem on

Windows 10 - eM Client 8.2.1659
For some days the SMTP server has been not accepting my outgoing messages with the following unclear message (that I report as it appears on the screen, including the line breaks and no error number code):
[SMTP] Failed to send message (Email body not accepted for the following reason:
"Message refused

I reinstalled eM Client, checked my pc with McAfee antivirus, disabled firewall, checked eM account settings, changed the SMTP setting. Everything useless … Some advice? Thanks.

Have you opened a support ticket with “”?

Thanks for your contributing.
Unfortunately Alice gives only an automatic support. In any case I followed their suggestion to change the PSW. No positive result. From the the message of error I suspect a virus or a malware in my PC, but McAfee and Malwarebytes gave a negative scan.

Try turning off your Anti-Virus software

What is “automatic support”?