Here is how to change your SMTP settings for Thunderbird:
Go to the menu, click tools and then account settings.
Now click outgoing server (SMTP)
Choose the outgoing server from the list you need to modify and then click edit.
Now a window will appear where you can modify Server name, Port and Connection Security. Both the settings must be changed depending on what your e-mail service supports. You can try different combinations.
Mail Server setting for Mac
You need to refer to your e-mail app’s documentation for info on how to use these settings.
Choose Preferences…from the menu.
Choose Accounts in the toolbar.
Click account you wish to verify.
Verify the account as well as the incoming Mail Server settings on the right.
Select Edit Server List from the Outgoing Mail Server pop-up menu.
Verify the Server Name setting on the right. If the Server Name is not correct, click Server Name box under Account Information and enter the correct server name.
Go to the Advanced option and then, verify the Advanced settings on the right.
Click OK.
