In your case it is not identities but POP3 hosts that you need to look at.  Go to Tools > Internet Options then open the Receiving(POP3) tab.  Remove or disable the POP3 hosts that you no longer need. 

Also, be aware of the settings at the bottom of the Receiving(POP3) window that control the checking of multiple POP3 hosts.

Finally, you may wish to go a step further and clean up any obsolete POP3 host definitions.  To do this click the Add button.  It will open a window in which you can work with all configured POP3 host definitions.  

I use PMail at home since 1996. It is my favorite mail client. I upgraded to 4.63 when it just appeared. I get lost identities in Tools/Identities list. List is just empty, only <Default> identity is shown. But identities work. When I click to "check POP3 mail" button - PMail checks all identities like they are available. Two of them are obsolete and give error messages each time. It is very annoying. Please help me edit identities and remove all obsolete identities.