You know who is sending it to you. ADD that person to your contact list to prevent it from accidently getting sent to the SPAM folder.
Check your Junk/SPAM/Undesirable folder and check if the message is there.
Check your Trask/Deleted message folder. That message may have been accidently deleted.
A web mail account gives you a few days. Regular e-mail retention is user defined with some somewhat generous default value.
Also, even if it's rare and geting rarer every day, an e-mail may take a few days to get to it's destination, altough it normaly takes only about a second or even less.
Electro
February 2012