On our hosting services shared between users, we apply limits to mail sent per second and per hour. This is to prevent a server being blacklisted and a single account causing problems for others.
These limits are:
- 1 message per second
- 3600 messages per hour (total)
Accounts which send more than 1 message per second, may be suspended automatically.
The limit of 3600 per hour still has the same per second limit but for accounts that exceed this will have their messages returned for exceeding the rolling 3600 limit.