Limits 
There is a 450 outgoing email hourly limit per domain.

If you send more than 450 emails per hour, most of the e-mails will bounce back with an “undeliverable error”. If this occurs, it will then take some time for your account to be able to send emails again. Therefore, we recommend waiting at least 1 hour after this issue occurs to begin sending email again.

Mailing Lists Rules 
1. Email lists must be throttled to a rate of no more than 1 email every 8 seconds. Sending 1 every 8 seconds would send 450 emails within 1 hour, keeping you at or below the 450 outgoing email limit per domain.

If your mailing list software does not allow you to throttle, you must switch to an application or script that will. We recommend PHPList, which can be found in your CPanel, under Quickinstall.

IMPORTANT: If you do not throttle and you try sending 450 emails, the server will try sending all of the emails in 1 single second, which is physically impossible. This will cause a very high load on the server and the entire server will be sluggish, potentially affecting your sites and service, until this sending process is completed. It is our job to keep the server up and running without being sluggish or experiencing issues. Anyone who causes the server's load to go high may have their email account suspended and the process will be terminated.

2. Mailing lists over 900 email addresses is only allowed to be sent to during off-peak hours to prevent high server loads. Off peak times qualify as all day Saturday and Sunday, and 1AM - 8AM Eastern Standard Time, Monday through Friday.

3. All email lists must be a “Double Opt-In list”. This means a user has subscribed for a newsletter or other email marketing messages by explicitly requesting it and confirming the email address to be their own.

Confirmation is usually accomplished by responding to a notification/confirmation email sent to the email address the end user specified. The double opt-in method eliminates the chance of abuse where somebody submits someone else's email address without their knowledge and against their will. You will not be permitted to mail any mailing list that you were given or purchased. In doing so, this will also be considered spamming and may result in just cause for suspension or termination of the offending account.

Email Scripts must be able to handle and document all information from a double opt-in list. This includes recording the sign-up IP address and date/time, double opt-in verification IP address and date/time, processing opt-outs (via web or email), and list removal on bounce backs. All opt-outs or bounce back removals must be handled in a timely manner, and outbound mail must be throttled to a maximum of 450 (four hundred fifty) emails per hour. If your account is found to be using a script that does not meet these requirements, Active Technologies reserves the right to suspend, terminate, or deactivate your script or account.

4. Sending of unsolicited e-mail will result in suspension or termination of the offending account. We take a zero tolerance stance against sending of unsolicited e-mail and other forms of spam.

. Any and all email lists MUST comply with all guidelines set forth by the United States government found at
http://www.ftc.gov/bcp/edu/pubs/business/ecommerce/bus61.shtm .

6. Active Technologies does not permit direct SMTP mailers such as Darkmailer or The Bat!. All mail should be sent through the local mail server/MTA for further delivery by the server and not directly by scripts.