Why servers get blacklisted
Why do email servers get blacklisted?
This has more to do with how and whom you send to, rather than how much. As long as you are sending to recipients who have expressly opted-in to receive your messages (but not through a 3rd party) and you include a clear and easy unsubscribe mechanism in every message, you should not have problems.
Even when following these guidelines, you can become blacklisted, and the main cause for this is usually recipient behavior. Often times a recipient won’t remember signing up to receive your emails and rather than using the proper route of following your unsubscribe directions, they will click the ‘Mark As Spam’ button in their email client or webmail account. Doing this generally reports the message as SPAM to their email provider which this results in negative impact to you and potential blacklisting. Obviously though this behavior cannot be prevented, which is why it is important to have a clear and simple unsubscribe mechanism that encourages recipients to unsubscribe appropriately.