Please note that in general we recommend you use a mailing list program if sending a single email to a large number of people rather than putting all addresses in the To, CC, or BCC fields of an email and sending it. Even if the email is not blocked by us there is a higher chance it will be filtered as spam on the receiving side.
cp.blacknight.com hosting packages:
The limit on the amount of people you can send an email to, and the amount of emails a single address can send in one minute, on our new plans depend on the hosting package you have. They are:
Minimus plan - maximum of 50 emails per minute, 500 per hour, 5,000 per day
Medius plan - maximum of 100 emails per minute, 1,000 per hour, 10,000 per day
Maximus plan - maximum of 100 emails per minute, 1,500 per hour, 15,000 per day
The maximum number of recipients on a single email is the same as the amount of emails you can send per minute. That would be 50 on a minimus plan, 100 on a medius, and 100 on a maximus plan.
The maximum email message size - including attachments, is 12MB.
On a VPS plan you aren't limited at all by us on what you can send email wise. You can change any default limits your mailserver might put in if you wish, or set up your own. The only limit is the hardware (CPU and RAM) limits on the VPS itself i.e. how many emails it can physically cope with.