The type can be one of the following:
register, verify, drop, email-change, passwd-change, passwd-request
Example:
/as services set template verify verify.tem
The filename is optional. It is relative to the root of the CR install, so if you have your file in db/mail/templates you should use "db/mail/templates/mymailtext.txt" as the filename used. If it is not specified, services will use a default mail template.