[sylpheed:37124] Re: Gmail accounts no longer accessible from Sylpheed?

I wrote on the 6th of June:

> And my Gmail account still works with Sylpheed without any
> changes!

But now it won't connect to my Gmail with the following log:

* creating IMAP4 connection to imap.gmail.com:993 ...
[13:21:29] IMAP4< * OK Gimap ready for requests from 178.176.72.8 i11mb37777293lte
[13:21:29] IMAP4> 1 CAPABILITY
[13:21:29] IMAP4< * CAPABILITY IMAP4rev1 UNSELECT IDLE NAMESPACE QUOTA ID XLIST CHILDREN X-GM-EXT-1 XYZZY SASL-IR AUTH=XOAUTH2 AUTH=PLAIN AUTH=PLAIN-CLIENTTOKEN AUTH=OAUTHBEARER AUTH=XOAUTH
[13:21:29] IMAP4< 1 OK Thats all she wrote! i11mb37777293lte
[13:21:29] IMAP4> 2 AUTHENTICATE PLAIN
[13:21:29] IMAP4< + 
[13:21:29] IMAP4> ****************
[13:21:29] IMAP4< 2 NO [AUTHENTICATIONFAILED] Invalid credentials (Failure)
** LibSylph-WARNING: [13:21:29] IMAP4 authentication failed.

** IMAP4 authentication failed.
[13:21:29] IMAP4> 3 LOGOUT
[13:21:29] IMAP4< * BYE Logout Requested i11mb37777293lte
[13:21:29] IMAP4< 3 OK Quoth the raven, nevermore... i11mb37777293lte
** LibSylph-WARNING: [13:21:29] Could not establish IMAP connection.

They are quoting from Poe, how impudent!
Do other users of Gmail experiece the same error?