I run VBulletin forum software that sends me email anyting something goes wrong with the sever etc. here. Could that cause me to get grey or blacklisted??
The email limit for free hosting is 100 emails per hour. If you exceed that limit for any reason - your account will be automatically greylisted. Admins can remove your account from the greylist - but should you send an incredibly excessive amount of emails in a short period of time or your emails contain a large amount of spam content, you may end up on the blacklist which they (Admins) will not remove your account from.
The point is, i dont send any, mainly because mail on these servers has been messed up for some time, however i cant control the mail im sent, from VB telling me that something is goofed up on X10. Oh well. what will be will be i guess.
If the site isn't up and running (that is, if PHP is down, or if your account stub on the server proper can't reach your files on the SAN, or crons can't run) then it can't attempt to send you mail at all, let alone two a minute for an hour.
My point is "If you exceed that limit for any reason" you can be put on the 'Blacklist'
IMO you would do better to use a 'on the Web' monitor that checks for Keywords on your site (page) - it will send you a alert (be sure to use a address like Gmail) when it goes down and when it is back up "for any reason"