I have the same problem as reported some days ago. I have used version 18.104.22.168. And as soon as I got an email with an attachment, mainly pdf-files, the program needs up to 10 minutes to start and the mimetypes.rdf file increases up to 500 MB or more. And the program crashes as it is not possible anymore to open emails containing an attachment. This is independent of using a notebook or USB device. It working sometimes to delete the mimetypes.rdf file, but this has worked out just a few times. Now, I changed back to 22.214.171.124 and everything is fine! What's wrong?