Well, you could use use the "dbtools" section of the CP (CP -> Tools & Info -> Database Tools -> SQL Command -> Query) and execute:
Code
UPDATE `ubbt_USER_PROFILE` SET `USER_ACCEPT_ADMIN_EMAILS` = 'On'

Note that the above query assumes your db prefix is "ubbt_"

I'd also like to state that by changing users who've opted out of mailings from your site, you may run into spam issues with your host... but to each their own.

I am a Web Development Contractor, I do not work for UBBCentral. I have provided free User to User Support since the beginning of these support forums.
Do you need Forum Install or Upgrade Services?
Forums: A Gardeners Forum, Scouters World
UBB.threads: UBBWiki, UBB Styles, UBB.Sitemaps
Longtime Supporter & Resident Post-A-Holic
VNC Web Services: Code Modifications, Upgrades, Styling, Coding Services, Disaster Recovery, and more!