Some days ago I found out something new about using convert task to convert mailboxes from one template name to another one.
The long story short:
if, for any (weird) reason, your mailboxes do NOT have template inheritance set (db properties->Design tab-> "Inherit design from master template" is blank), issuing a classic "load convert ..." WILL NOT automatically set the new template name to all your mailboxes.
Use the "-inherit" command line switch as in "load convert -inherit mail\ * mytempl.ntf "
I copied a standard mail template to develop a new custom mail template: the new template did not have set the db title (was blank) and ALSO the design property that it was a master template!
I fixed the db title but did not realized that the template name was blank too:
when I applied the custom template to all mailboxes, I reset all inheritance to blank.
No problem, I set the db template name to a custom name and reapplied it to all mailboxes BUT is was unsuccessful: inheritance was still blank.
Later I issued "load convert -inherit mail\ * * mytempl.ntf" and all was fine.