missing plain authentication?

[Ross Boylan]

I'm setting up a new Cyrus 2.2 installation under Debian, and noticed
this peculiarity when running imtest from a user account:
------------------------------
$ imtest
WARNING: no hostname supplied, assuming localhost

S: * OK corn Cyrus IMAP4 v2.2.13-Debian-2.2.13-3 server ready
C: C01 CAPABILITY
S: * CAPABILITY IMAP4 IMAP4rev1 ACL QUOTA LITERAL+ MAILBOX-REFERRALS NAMESPACE UIDPLUS ID NO_ATOMIC_RENAME UNSELECT CHILDREN MULTIAPPEND BINARY SORT THREAD=ORDEREDSUBJECT THREAD=REFERENCES ANNOTATEMORE IDLE AUTH=CRAM-MD5 AUTH=DIGEST-MD5 AUTH=NTLM SASL-IR
S: C01 OK Completed
C: A01 AUTHENTICATE CRAM-MD5
-------------------------------------------------------------------
Shouldn't AUTH=PLAIN appear on that capability list?  I was able to
login using CRAM-MD5.

My imapd.conf includes
allowplaintext:: yes
allowapop: no
sasl_minimum_layer: 0
sasl_pwcheck_method: auxprop
sasl_auxprop_plugin: sasldb

I have not set sasl_mech_list.

Ross Boylan