Hmm... That should not be required. Probably there's a bug in some other place.

but when you change it in kolab-webadmin, it updates both auto_form_fields and form_fields as well.
can you reproduce that?

I confirm this may happen for fields with "Generated" value and we should probably fix that. Anyway, setting type in auto_form_fields if it's already specified in form_fields is redundant. Did you find any issues when it's not set in auto_form_fields?

Yes; this is my scenario:

vanilla install of kolab.
edit kolab.conf:
remove all secondary emails, so this remains:
secondary_mail = {

}

service kolabd restart

Now create a user without secondary mail addresses.
looks good.
Now edit the user, add a secondary mail address.
looks good.
Edit the user again, remove the secondary mail address, save.
Open the user again, but the secondary mail address will still be there.

If you check in the settings, kolab user, attributes, alias: it shows text instead of list.
if you don't change anything, and just click "submit" (Absenden in German) at the bottom of the screen, this will fix the problem.

Now check in mysql: auto_form_fields and form_fields will have type:list, and optional:true.