says the log, thus making master kmail kaputt! Maybe wrong component though
I guess I'm seeing this too today on my f25 box with kmail-16.12.2, unable to setup google mail account.
If you have self-compiled kdepim-runtime and you installed it into a custom (non-/usr) prefix, then you must manually copy libkdexoauth2.so (from $prefix/lib/sasl2) to /usr/lib(64)/sasl2 - unfortunately libsasl ignores environment variables and only looks for plugins into /usr.
Turns out in my case I needed to set https://www.google.com/settings/security/lesssecureapps first. Dan helpfully pointed out (on irc) that future releases of kdepim will include an OAuth authentication plugin, so this will no longer be necessary.
I'm not sure why this is resolved ... I've been hitting this continually in KMail 5.5.3 ever since I've upgraded to Kubuntu 17.10. It seems to happen quite consistently when initial authentication times out and needs to be refreshed. It can be fixed by switching the accounts offline, then back on, but is a *serious* pain.