Description of problem:
Evolution slow down or hang after some editing of message rules.
The resulting message rules file has a lot of duplicate lines.
I'm not really sure. With my rules just doing a few mods here and there seems to make it happen.
Created attachment 1036280 [details]
File gotten after the fact from: .config/evolution/mail
Thanks for a bug report. I can reproduce it too, for example when using filter rules like: [Subject] [Contains] [text]. This is not a Fedora specific issue, thus I move this upstream for better visibility. Please see  for any further updates.
evolution-mapi-3.16.3-1.fc22, openchange-2.2-7.fc22, evolution-ews-3.16.3-1.fc22, evolution-data-server-3.16.3-1.fc22, evolution-3.16.3-2.fc22 has been submitted as an update for Fedora 22.
Wow! Incredibly fast is becoming your "as usual"... :)
Since in  you suggest that people should clean the configs by hand, for those who want an easy clean-up I suggest to use uniq as in:
uniq '~/.config/evolution/mail/filters.xml' > uniq.tmpfile
mv uniq.tmpfile '~/.config/evolution/mail/filters.xml'
Uh! Sorry. Wrong quotes. The lines shoud be without quotes:
uniq ~/.config/evolution/mail/filters.xml > uniq.tmpfile
mv uniq.tmpfile ~/.config/evolution/mail/filters.xml
evolution-mapi-3.16.3-1.fc22, openchange-2.2-7.fc22, evolution-ews-3.16.3-1.fc22, evolution-data-server-3.16.3-1.fc22, evolution-3.16.3-2.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.