[fetchmail] Problem with User ID during server login

Our ISP uses our email addresses as our user ID during POP3
authentication.  My login looks like "name(_at_)domain(_dot_)com".  The ISP's 
mail
server is a different domain, (our email addresses are aliased), so
mailserver.differentdomain.com.  

 

fetchmail always appends the user id to the server name and I get
name(_at_)domain(_dot_)com@mailserver.differentdomain.com which of course fails
authentication.  How can I control whether fetchmail mangles the user id
I provide?

 

Thanx!