[threadbare]

The rule is greater than 50 individual messages in an hour period. the abuse dept will put a block on any user who exceeds this limit 3 times. These users will then be contacted.

Providing all is legit and ppl genuinely need to send that volume of mail, they can add the IP address to the White list which will have no restrictions.

These users can then send their mails without being flagged up and blocked