Memory corruption during sleep
Yesterday I put my laptop to sleep (on AC power) while I went to the christmas party of a company I worked for.
After returning, I couldn’t read my email any more; dovecot would segfault after login. Restarting dovecot didn’t help, but a reboot helped.
Sounds to me as if during sleep, some kernel cache of the dovecot application was corrupted (read only memory; cached by the kernel, which is why it survived the restart of dovecot).
Whoa, this is like Windows. Rebooting the computer actually fixed something!