can be authenticated but can't login?

[Chowroc at 163.com]

I create a user with cyradm and test like this:

localhost.localdomain> lm
user.cu01 (\HasNoChildren)

# sasldblistusers2
saslu01 at zouben.org: userPassword
cu01 at Chowroc: userPassword
Lu41 at dm04.com: userPassword
vdmu01 at vdm.com: userPassword
vu at vacuum.com: userPassword
cyrus at Chowroc: userPassword

# imtest -a cu01 localhost
S: * OK Chowroc Cyrus IMAP4 v2.1.16 server ready
C: C01 CAPABILITY
S: * CAPABILITY IMAP4 IMAP4rev1 ACL QUOTA LITERAL+ MAILBOX-REFERRALS NAMESPACE UIDPLUS ID NO_ATOMIC_RENAME UNSELECT CHILDREN MULTIAPPEND SORT THREAD=ORDEREDSUBJECT THREAD=REFERENCES IDLE AUTH=DIGEST-MD5 AUTH=CRAM-MD5
S: C01 OK Completed
C: A01 AUTHENTICATE DIGEST-MD5
S: + bm9uY2U9IjhnYW9FajRQMUxDdzhHeDZCdkJyZ3cvQUNiRnZrdEU1WDBYVURNa3NDOTQ9IixyZWFsbT0iQ2hvd3JvYyIscW9wPSJhdXRoLGF1dGgtaW50LGF1dGgtY29uZiIsY2lwaGVyPSJyYzQtNDAscmM0LTU2LHJjNCxkZXMsM2RlcyIsbWF4YnVmPTQwOTYsY2hhcnNldD11dGYtOCxhbGdvcml0aG09bWQ1LXNlc3M=
Please enter your password:C: dXNlcm5hbWU9ImN1MDEiLHJlYWxtPSJDaG93cm9jIixub25jZT0iOGdhb0VqNFAxTEN3OEd4NkJ2QnJndy9BQ2JGdmt0RTVYMFhVRE1rc0M5ND0iLGNub25jZT0iRnBIMUdJdm1kRkRzNnhYendhT0tCYnJvYnBtRDkyTTkvd1YrcUl2aHZVaz0iLG5jPTAwMDAwMDAxLHFvcD1hdXRoLWNvbmYsY2lwaGVyPSJyYzQiLG1heGJ1Zj0xMDI0LGRpZ2VzdC11cmk9ImltYXAvbG9jYWxob3N0LmxvY2FsZG9tYWluIixyZXNwb25zZT04ZDE4MjAzMDAyYjc1ZDIwZDFiYWM1MzYyNGJiZGEwZQ==
S: + cnNwYXV0aD0yZmEzZjYwN2JkMTlmOGZhZTMxOTk3ODQ3ZDhjOWI1Yg==
C:
S: A01 OK Success (privacy protection)
Authenticated.
Security strength factor: 128

# imtest -m login -a cu01 localhost
S: * OK Chowroc Cyrus IMAP4 v2.1.16 server ready
C: C01 CAPABILITY
S: * CAPABILITY IMAP4 IMAP4rev1 ACL QUOTA LITERAL+ MAILBOX-REFERRALS NAMESPACE UIDPLUS ID NO_ATOMIC_RENAME UNSELECT CHILDREN MULTIAPPEND SORT THREAD=ORDEREDSUBJECT THREAD=REFERENCES IDLE AUTH=DIGEST-MD5 AUTH=CRAM-MD5
S: C01 OK Completed
Please enter your password:
C: L01 LOGIN cu01 {4}
S: + go ahead
C: <omitted>
S: L01 NO Login failed: authentication failure
Authentication failed. generic failure
Security strength factor: 0

Thus, if I use mutt to get the mails with POP3, I get "SASL authentication failed". 

Is there anyone can tell me what's wrong?

thanks.
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