>I would like to know what policy to follow terms of the number of recipients 
>who permitís send an e-mail. 
>I do not currently have limited, but I'm thinking about putting it at 70. 

Years ago, spammers loaded up the to: and cc: fields with dictionary attacks, 
10s or 100s of recipients, but I haven't seen that very much recently.  So a 
low limit is not really today much of a defense.

Besides limiting the number of recipients per TO: or CC: field or header, SMTP 
protocol also has a limit of max header line length, which some MTAs like 
postfix allow lowering the limit of charatcers to 256 or whatever.  All 
addresses up to 256 are accepted, but above 256, the recipients are silently 
truncated.  oops

Legit users who put 10s of recipients in to: and cc: are often forwarding jokes 
or articles to their list of friends.  Some of my friends do it and their to: 
lists have easily 20, 30 recipients.

I've just done some research over a week's maillogs for one of my IMGate 
clients on this very question and found, again, that nearly all msgs had 1 
recip.   Here are the number msgs with how many recips, 

nrctp = number of recipients:

msgs  recips
73072 nrcpt=1
1476 nrcpt=2
 308 nrcpt=3
 114 nrcpt=4
  96 nrcpt=8
  75 nrcpt=5
  22 nrcpt=11
  21 nrcpt=12
  19 nrcpt=6
  16 nrcpt=15
  15 nrcpt=13
  13 nrcpt=7
  11 nrcpt=17
  10 nrcpt=16
   8 nrcpt=20
   7 nrcpt=10
   4 nrcpt=9
   4 nrcpt=18
   2 nrcpt=14
   1 nrcpt=83 !!!!!!!!!!
   1 nrcpt=50
   1 nrcpt=26
   1 nrcpt=22

These were all msgs that "passed clean" in IMGate's spamassassin, ClamAV, and 
other policies so were legit and raised no complaints.

Now above, these were number of recipients per SMTP session, not necessarily in 
the TO: or CC: fields, meaning that a list server may have consolidated many 
single TO: into one SMTP session.

For setting any limits for any specific population of recipients, the best is 
to analyze the logs and come up with a report like above to see what limit 
would be reasonable.  If the number of recips isn't causing any problems, then 
I wouldn't "fix" a non-problem.


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