default_destination_recipient_limit parameter (default:
50) controls how many recipients a Postfix delivery agent will send
with each copy of an email message. You can override this setting
for specific Postfix delivery agents. For example,
"uucp_destination_recipient_limit = 100" would limit the number of
recipients per UUCP delivery to 100.
If an email message exceeds the recipient limit for some
destination, the Postfix queue manager breaks up the list of
recipients into smaller lists. Postfix will attempt to send multiple
copies of the message in parallel.
IMPORTANT: Be careful when increasing the recipient limit per
message delivery; some
smtpd(8) servers abort the connection when they
run out of memory or when a hard recipient limit is reached, so
that the message will never be delivered.
smtpd_recipient_limit parameter (default: 1000) controls
how many recipients the Postfix
smtpd(8) server will take per
delivery. The default limit is more than any reasonable SMTP client
would send. The limit exists to protect the local mail system
against a run-away client.