LDAP Authentication: samaccountname token not being replaced with actual samaccountname value when generating email address

We use Active Directory and do not use the mail field, so I need to generate the email address from a template. We use the person's logon name, which is equivalent to sAMAccountName, in the template. So I want to use something like [samaccountname]@example.com. The only problem is when the user logs in for the first time and gets auto-created, the generated email address is exactly [samaccountname]@example.com, rather than jdoe@example.com. So for some reason sAMAccountName isn't being brought along with the returned LDAP information. I tried switching the template to [cn]@example.com and that get's replaced with John Doe@example.com, which is what I expected.

Any clue as to what the problem could be here? This is kind of a show stopper.