The proxy behaviour appears slightly changed in 2.0.0.22 such that if you have user proxy for all protocols, it tries to use a proxy for connections on port 110 and doesn't fall back the way it use to.

Didn't look too closely when I discovered setting HTTP and SSL proxy only (and unticked the all other protocols box) got the users email fetched, and that these settings better reflect the configuration in use. But this misconfiguration broke between 2.0.0.21 and 2.0.0.22 so I doubt I'll be the only one seeing this.