-relies on the SIZE parameter on the MAIL command, which may be inaccurate or
-completely missing. You can follow the limit &'m'& in the configuration with K,
-M, or G to specify limits in kilobytes, megabytes, or gigabytes, respectively.
+relies on the SIZE parameter specified by the client in its MAIL command,
+which may be inaccurate or completely missing. You can follow the limit &'m'&
+in the configuration with K, M, or G to specify limits in kilobytes,
+megabytes, or gigabytes, respectively.
+
+The &%per_rcpt%& option causes Exim to limit the rate at which
+recipients are accepted. To be effective, it would need to be used in
+either the &%acl_smtp_rcpt%& or the &%acl_not_smtp%& ACL. In the
+&%acl_smtp_rcpt%& ACL, the number of recipients is incremented by one.
+In the case of a locally submitted message in the &%acl_not_smtp%& ACL,
+the number of recipients is incremented by the &%$recipients_count%&
+for the entire message. Note that in either case the rate limiting
+engine will see a message with many recipients as a large high-speed
+burst.