Make sure TLS 1.0 & 1.1 is disabled on all Servers, Machines, Web-Tier, Print Server, Etc. Since our Version 12.2.17, the software has been standardized to use TLS 1.2 for emails. There likely is a location that is still trying to use TLS 1.0 & TLS 1.1 that has not been disabled.
"As of October 31, 2018, the Transport Layer Security (TLS) 1.0 and 1.1 protocols are deprecated for the Microsoft 365 service." I was able to locate a Microsoft release on 2/16/2023 regarding this. Disabling TLS 1.0 and 1.1 for Microsoft 365 - Microsoft Purview (compliance) | Microsoft Learn
To disable TLS 1.0/1.1 and enable TLS 1.2 by Default, please find included how to accomplish this: How to Remove TLS 1.0 and 1.1.