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From my researching this forum and bugzilla, I believe that Zimbra 7.1.x does not support SMTP AUTH(Cram-MD5 with LDAP).
Is this my understanding correct?
In order to support this, at least Zimbra LDAP have to have plain text password in the ldap database. Currently the password is stored as hashed strings.
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SMTP AUTH (Cram-MD5 with LDAP) in 7.1.x 
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