sendmail, 4th Edition

r=

Maximum recipients per envelope V8.12 and later

Normally, sendmail limits the number of outbound SMTP RCPT To: commands allowed per session to the size of the DEFAULT_MAX_RCPT compile-time macro (MAX... on page 120), which is defined as 100 in sendmail/conf.c. When delivering an envelope, sendmail will deliver only the maximum number of recipients on the first try. Any that are left over will be deferred until a later delivery attempt (usually during the same queue run).

One problem with piling many recipients into a single envelope is that some sites on the Internet refuse to accept mail when the envelope contains too many recipients. Another, but opposite, problem is that some sites can accept more than 100 recipients per envelope, and you would prefer to send them as many as they can handle in a single transaction.

One way to limit or expand the number of recipients allowed in an envelope is to use this r= delivery agent equate:

r=val

If val is set to a nonzero value, it changes the limit on the number of recipients allowed to the value specified. If val is less than or equal to zero, the limit is set to the value of the DEFAULT_MAX_RCPT compile-time macro (MAX... on page 120).

Some delivery agents provide mc macros with which to add an r= equate. For example, the following mc configuration lines add that default to the various smtp delivery agents:

define(`SMTP_MAILER_MAXRCPTS', `80')    ← this must be
MAILER(`smtp')                          ← before this

See the section describing a particular delivery agent ...