In VPOP3 a Mail Sender tells VPOP3 how to send outgoing messages.
To access the Mail Sender settings, click on the Mail Connectors button on the top of the VPOP3 settings screen, then see the Mail Senders section of the tree on the left of the screen.
To add a new Mail Sender, click on the Add New option under the Mail Senders section (note that this will add a Connection as well).
To edit or view a Mail Sender, select the relevant Mail Sender, then look at the settings in the right-hand side of the screen.
To delete a Mail Sender, select the relevant Mail Sender, then click on the Delete button at the top-right of the Mail Sender settings.