I don't use monthly subscriptions in WoW so I'm always aware when I'm buying more game time so I constantly determine if it's worthwhile to toss down $15 again and again. As a result, I'll occasionally let my account be frozen for a couple weeks at a time until I feel like playing again.
With my many alts, I abuse the mail system for cheap communal bank slots, and I have a few dozen mails filled with this or that going between my characters. My account has lapsed before while I've had stuff in transit, but I never bothered to pay attention to what happened to my items. What happens to my in-game mails when my account is in a "Frozen" state? Does the 30-day mail timer keep ticking down until they rot or are returned? Does the clock freeze? Would I still get auction-house mail for a successful sale, etc?