For the last few days, a spammer has been sending out emails using my address in the From field. Therefore I'm getting thousands of "Mail Delivery Failed" emails per day.
I've set up a filter to move emails to a separate folder if they are from senders such as "Mail Delivery System". The filters work when I'm receiving multiple emails per minute. However, when I turn on the PC in the morning and open Thunderbird, what typically happens is that it downloads 1000 or more new emails in the inbox, then starts moving them to the other folder at a very slow rate (about one per second). Not only does this take an extremely long time, but also it typically gets stuck after a while, stops processing the filters and starts running extremely slowly, e.g. taking 30 seconds to open the message filters window. I then have to restart the software. After restarting, if I run the filter manually on inbox, it moves all the emails very quickly.
