@dhulappar5172   

Are you using  SMTPS with connection to server for Microsoft office365 (smtp.office365.com) ?  Can you uncheck that option   in Email account configuration and test connection ?

The SMTP server for Microsoft office365 (smtp.office365.com) uses StartTLS protocol for encrypting emails, and Pega 8.x has StartTLS enabled by default. So it is not required to check the SMTPS checkbox in the email account ruleform when using the port 587.

If you are using gmail, then you can use "465" as a port no. and then check your connectivity.

Additional reference: https://docs.pega.com/data-management-and-integration/84/creating-email-account#:~:text=The%20following%20default,465%20(SMTPS)

https://support.microsoft.com/en-us/office/pop-imap-and-smtp-settings-8361e398-8af4-4e97-b147-6c6c4ac95353#:~:text=Server%3A%20smtp.office365,Encryption%3A%20STARTTLS

 Check  property under SysAdmin\Dynamic System Settings that needs to be setup with true value

Pega-IntSvcs | Email/DisableSecuritySTARTTLS | true

If you need further help I would suggest that you log a support incident:

Can you provide the information available when you expand the 'Debugging information' section of the test connection?

Can you also check the logs to see if there is an error and stack trace there and provide that? 

Could you please create a log category and add the below logger,

• com.pega.pegarules.integration.engine.internal.services.listener.ListenerStateManagerImpl
• com.pega.platform.integrationengine.client.email.PegaEmailClient
• Rule_Obj_Activity.pySMTPConnectivity.Embed_ISInfrastructureValidate.Action
• Rule_Obj_Activity.SMTPConnectivity.Data_EmailAccount.Action
• Rule_Obj_Activity.POP3orIMAPConnectivity.Data_EmailAccount.Action
• Rule_Obj_Activity.pyPOP3OrIMAPConnectivity.Embed_ISInfrastructureValidate.Action

Once the log category is created go to Admin studio à Log category tab and enable the log setting to debug.