I am using it to attempt to DL mail from two Yahoo! mail accounts. When I started this "cleanup" project, the nastier of the two had probably 10-20 folders with 500-1000 messages each in them, and the main inbox had probably about 10,000 messages in it. In each folder, let's say maybe half the messages were marked "read" and the rest not.
At first it would crash and time out repeatedly during the course of downloading new messages. After reading a couple blog comments or forum posts or whatever which indicated to me that YPOPs might have trouble dealing with extreme numbers of messages, I went into the Yahoo! Mail web interface and deleted a bunch of stuff in there (nightmare). Got my inbox down to .. say .. 1500 messages, and the folders down to a couple hundred each. This did not fix the crashing behavior.
After repeated retries, I think I have all the messages downloaded (but maybe not -- see my forthcoming post), and now it just crashes after Thunderbird displays the "There are no new messages on the server." message.
My second account has seemingly manageable numbers of emails in it -- like maybe 100-150 in the main inbox and 20-50 in each of 3 or 4 folders -- but it exhibits the same behavior.



