There is a misfeature in mailcheck applet.  When it is checking a POP
server, it occasionally gets a connection error.  This is normal (it
happens in other programs as well, usually trying again will work).  The
problem with mailcheck is that it then disables automatic checking for
email and it must be manually re-enabled.  It would be better if it perhaps
displayed a different image to notify the user that something is amiss but
it should not alter its settings.  It can keep trying and failing.  That is
better than having to manually restore the settings for a temporary
connection error.