If you want to send letters, gifts, tapes, or anything else to nsync you can send it to:

*N SYNC
Official International Fan Club
P.O. Box 5248
Bellingham, WA 98227
USA

If you want to email the guys you can do so by writing to them at [email protected] you will probably just get a automatic response but who knows! You might get really lucky and catch one of the guys on their off time! They might just email back!  Good Luck!