Could you please add a line at the very end of these mails with:

To unsubscribe click: www.somelink.com

As it is it seems that some people have trouble getting off the list after they sign up. Because my spam filter keeps sending phenixbb mails into the spam folder. Which is likely because someone out there keeps flagging them as spam. 

If there's a link like that then gmail will even offer to attempt to unsubscribe for you. 

Just a thought. 

Cheers,

Morten