While sending an email you may get error as “The server you are connected to is using a security certificate that cannot be verified. The target principal name is incorrect.”
This error usually caused by a mismatch in enabling SSL and the port number as entered in your Outlook account settings.
You can solve this issue for outlook 2010 using below mentioned steps.
Step 1: Open outlook and click on File tab. Go to Account settings and click on the pop-up box.
Step 2: Go to Change option. Now you can see the email accounts which you have setup. Double click on the account which you wish to view.
Step 3: Click on More settings option in the lower right corner and click on the Outgoing server tab. Then click on Advanced tab.
Verify that you are using the correct ports for the incoming and outgoing mail server.
Below are the port numbers for Non-SSL connections:
Incoming Port number (if using POP): 110
Incoming Port number (if using IMAP): 143
Outgoing SMTP: 587
The box "Use the following type of encrypted connection" should have none selected.
If you are using SSL / Encryption, the port details will be different:
SSL enabled incoming POP: 995
SSL enabled incoming IMAP: 993
SSL enabled outgoing SMTP: 465
The box "Use the following type of encrypted connection" should have SSL/TLS selected.