Sorry, I kind of forgot about lemmy or a few days. In Thunderbird, I create a new dedicated folder, use Tools --> Message Filters. I then can add the desired filter (something like must cotain at least ‘host.tld’ in sender) and make it move all filtered mails into the previously created folder. I just checked, it works (you can also specify when that filter should be executed (e.g. when getting new mails or every 10 minutes) and the folder with the filtered mails also shows up in FairMail on Android. Better description: …mozilla.org/…/organize-your-messages-using-filte…