Change All Existing Members Subscription Mode to Daily Email

[ngkong]

I wonder if there is a way to force all existing members to receive daily subscription email (thread reply). My forum used to very active and has quite a lot of members, i hope by doing this will bring back old members to the forum once again. What i found in vbull options is Default Subscription Mode for new registration, not for all members.

Is it complex job to do? i mean does it only need a mysql table edit, or needs multi linked table to be edited by a script. is it enough to just edit value of "autosubscribe" field in user table?

thanks