Correct JRE version should be installed compatible with the JIRA version on the Server where JIRA is installed.
Go to the Path for JAVA_HOME is configured. You can verify at your command prompt Admin mode with:
It would look something like this on the Server where JIRA is installed.
Import POPS certificate on Server for mailbox connectivity with JIRA:
The certificate would be created by your internal CA. You can place it at an accessible path on the JIRA Server. Use the below command:
C:\Program Files\Atlassian\JIRA\jre\bin> keytool -import -alias rootCA -keystore "C:\Program Files\Java\jre1.8.0_91\lib\security\cacerts" -trustcacerts -file "E:\Certificates\POPS.cer"
Download SSLPoke.class. Place this class at the above bin path.
Diagnose connectivity with the following command:
C:\Program Files\Atlassian\JIRA\jre\bin> SSLPoke mailserver.example.com 995
995 is the port for Secure POP and the Server name would be your On Premise Exchange Server name.