When using host auth mode the user is given a default email address

When using host auth mode the user is given a default email address
based on the gecos field from the passwd file which is usually
"firstname_lastname" this results in the user not being able to receive
mail to their default username address.
To rememdy this when the user logs in for the first time we now create
the users vCard as normal and then add an alias to the vCard.
The alias is username@domain as opposed to firstname_lastname@domain.
We only add the alias if it would differ from the original address.
We only do this in host auth mode.