Command - /NickServ SET MAXMEMO
Usage   - /NickServ SET MAXMEMO [number of memos]
This command limits the maximum memo(s) a nick will be able to have.
When you reach your maxmemo limit users who try to send you a memo
will get a message saying your memobox is full.
Note: You must be identified to NickServ in order to use this command.
Example(s):
/NickServ SET MAXMEMO 10
/NickServ SET MAXMEMO NONE