I have seen this problem posted several times without a solution and having fixed it, I am making the effort to let all know the answer. Here is the error / problem: "The RETR command did not succeed. Error retrieving a message. Mail server pop-server.woh.rr.com responded: no such message." I had this happen some time ago on another pop on RR mail server and logging in via Web Mail and deleting the emails worked BUT.. It happened again on another pop account and it did not work.. So... I nuked the pop via the master account and re-added it.. nothing so, I ran check disk thinking a FAT corruption NOPE, I restored a MOZBACK of Thunderbird from like a month ago Ziltch.. I called useless RR support and nothing! FINALLY *Scratching Head*.. In there change your Junk mail options to "delete the email". I had one junk email stuck in there and after refreshing that page..That one Junk Email was gone and THEN Thunderbird worked checking that pop.. WAHLAH! I hate when the simplest of things do not work and it pissed me off nobody had the answer.. HERE YOU ALL GO! :) Leda937@woh.rr.com