Quoting Stephen Feyrer <steve@toth.org.uk>:
Hi.
I'm trying to test EXTERNAL AUTHENTICATION in Dovecot. To do this I
first configured Thunderbird and Opera to use my server, neither of
them were successful. As a result I contacted both organisations to
enquire if they supported EXTERNAL AUTHENTICATION in their products.
Thunderbird responded and said yes. However, on closer inspection
my contact at Thunderbird identified that support for EXTERNAL
AUTHENTICATION was poor at best and then only in SMTP. From that
point on, my contact has been trying to implement support in
Thunderbird.
[snip]
- OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID
ENABLE AUTH=EXTERNAL] Dovecot ready. 01 AUTHENTICATE EXTERNAL
- 01 list "" * 01 NO [ALERT] Invalid base64 data in continued response
This is incorrect. You need this:
C: 01 AUTHENTICATE EXTERNAL S: + C: S: 01 OK
(you are missing the empty response back to the server)
Or, better yet (since SASL-IR is available):
C: 01 AUTHENTICATE EXTERNAL = S: 01 OK
michael