1. Launch Exchange Management Shell
Click on Start and then expand Exchange Server 2019 and right click on the Exchange Management Shell and select "Run as Administrator"
2. Type in command
Type in the command: Get-popsettings -Server EX2019A | fl
3. Type in command
Run the following command to set the pop internal settings: Set-PopSettings -server EX2019A -InternalConnectionSettings "pop3.thexchangelab.com:995:SSL","pop3.thexchangelab.com:110:TLS" -X509CertificateName pop3.thexchangelab.com
4. Type in command
Run the following command to set the pop external settings: Set-PopSettings -server EX2019A -ExternalConnectionSettings "pop3.thexchangelab.com:995:SSL","pop3.thexchangelab.com:110:TLS" -X509CertificateName pop3.thexchangelab.com
5. Type in command
Run the following command to set the X509: Set-PopSettings -server EX2019A -X509CertificateName pop3.thexchangelab.com