Spammers sometimes encode URLs so that they cannot be detected by spam filters. The following are examples of deceptive URLs:
http://7763631671/domainname.htm
http://0xCeBF9e37/domainname.htm
http://0316.0277.0236.067/domainname.htm
http://3468664375@3468664375/o%62s%63ur%65%2e%68t%6d