Personally I'd use

ADD listname DD=X PW=password
//X DD *
user1@host His Name
user2@host Her Name
/*

If you don't use QUIET ADD and don't specify IMPORT, this works just
as if you had sent individual ADD commands for each user in the DD.
If you don't have a "real name" for each user, just use an asterisk,
e.g.,

ADD listname DD=X PW=password
//X DD *
user1@host His Name
user2@host *
/*

Nathan