It looks like a dovecot update in rawhide has broken imaptest. [root@test-rawhide ~]# imaptest imaptest: symbol lookup error: imaptest: undefined symbol: base64_encode As far as I can tell, it just needs a rebuild (or rather, a rebuilt version does appear to at least run on rawhide). On IRC we had discussed now dovecot maintains no ABI stability, and mentioned having the most basic of %check sections: %check %buildroot/%_bindir/imaptest --help just to make sure the result still runs. Unfortunately this would not have made any difference here because a rebuild fixes the problem. Koschei wouldn't notice. The only option I see is hardcoding a dependency on the specific dovecot version, but that would probably lead to breakage even when a rebuild isn't necessary.
Thank you for the report. It's sad to see that Dovecot doesn't maintain any ABI stability even during patch-level releases.