Upgrades are downgrades

I made the mistake of upgrading my mail client the other day. For reasons that defy my understanding, it's interaction with one of the mail services I use changed - Eudora 6.0 read the mail just fine, and 6.1 wouldn't. I sent some time looking at the failure messages, and realized that it had a wild idea as to what the server name was - I had included the www. in the host name, and Eudora suddenly was baffled by that. Removing the leading www. solved the problem. Now back to my 200 inbound messages....