Hello!
Unfortunately, I have a very strange problem and I couldn't find any solution after hours of searching the logs and the internet.
Operating system: Ubuntu 16.04.3 LTS
Plesk version: Plesk Onyx v17.5.3_build1705170317.16 os_Ubuntu 16.04 (Plesk Onyx 17.5.3 Update #20)
Mail software: none...