When we have to make sure that your newsletters arrives as quickly as possible through the eye of the needle to your recipients' inboxes, the main factor is in our opinion dialogue with administrators in the other end.
Often when you have large amounts of e-mail to deliver, you will run into both temporary but also permanent blocks in different systems at your recipients. Thus it is important that you as sender makes sure to open the dialogue with the service providers before it turns into a problem.
As a basis for dialogue we have a separate, technical website targeted for the administrators that may receive e-mails from our customers. It is from that website our operations staff handles inquiries regarding special measures regarding delivery, e.g. volume and speed.