@full does not seem to get assigned anything. I am guessing you meant

  print MAIL "$#full messages have been deferred in the past $ttime mi
+nutes\n";
[download]

to say

print MAIL "$#log messages have been deferred in the past $ttime minut
+es\n";
[download]

I would also change

  print MAIL "@log";

to

 
  foreach ( @log ) {
     print MAIL "$_\n\n";
  }
[download]

to make your output easier to read. I would add a couple other newlines and a rundate just to make things easier to read on the mail.

Finally, the die statement if you get deffered within a certain time.

  if ($ttime == 0) {die ("deferred messages ocurred withing 1 minute o
+f each other\n")};
[download]

if you run this from a cron job, how would people know if there was a problem? Do you just keep this around and run it if the network seems slow?