In Tally.ERP 9, if you face the mail server connection failure in Tally Erp 9 issue, then it might be due to the email request being forwarded to the wrong port. It might also occur if the outgoing e-mail server is blocked by your computer’s firewall.To solve this issue, exclude your Outgoing email server port from your computer’s firewall or allow access to the Outgoing mail server port by adding it to your computer’s firewall.
Steps to add a port to the Windows firewall:
For the Windows 7 computer: