Pro:
"Inbox" is good
Could mean "In Boxes"
Con:
The -es kills it for me
.info doesn't really fit it
Would probably be hard to monetize
The best I can think of is an informational minisite about spam, scams, viruses, phishing, etc. Perhaps it could be a directory of free email services. $x undeveloped. Developed for revenue, it could pay back its renewal fee (when that arrives) and cover some of your hosting.