MaxRecipientsPerMessage
Maximum recipients per envelope V8.10 and later
When sendmail receives email via
SMTP, it gathers its list of envelope recipients
from the RCPT To:
command. In that command, two envelope recipients
might be specified (and acknowledged) like
this:
RCPT To:<userA@your.host.domain> 250 2.1.5 <userA@your.host.domain>... Recipient OK RCPT To:<userB@your.host.domain> 250 2.1.5 <userB@your.host.domain>... Recipient OK
Here, each RCPT To:
line tells sendmail to deliver
a copy of the message to each recipient specified in
that line. Each shows the local
sendmail acknowledging each
recipient.
One method of spamming is to list thousands of
recipients for each message—that is, to specify
thousands of RCPT
To: commands, causing
sendmail to deliver a copy of
the message to thousands of recipients. As an
antispam measure, V8.10
sendmail introduced an option
to limit the number of recipients that can be
specified for a given envelope. Called MaxRecipientsPerMessage,
that option is used like this:
O MaxRecipientsPerMessage=limit← configuration file (V8.10 and later) -OMaxRecipientsPerMessage=limit← command line (V8.10 and later) define(`confMAX_RCPTS_PER_MESSAGE', `limit') ← mc configuration (V8.10 and later)
The limit tells
sendmail the maximum number
of recipients it will accept for the current
envelope. Any that are specified beyond this limit
cause sendmail to acknowledge
with this message:
452 4.5.3 Too many recipients
A 452 SMTP acknowledgment tells the sending machine to ...
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