Basic IP Allocation

When you set up a new mail server, you soon have to decide how many IP addresses to send from. The answer depends on how much mail you send each day, and using more addresses than your volume supports can harm your reputation.

Who this guidance fits

The figures below assume that all of your mail is one kind, so you have no reason to keep separate reputations on separate IP addresses. If you do need that separation, start with Advanced IP Segmentation and Allocation.

They also assume that your goal is to deliver mail that recipients want and expect. For mail that recipients do not want or expect, following this guidance can lower delivery instead of raising it, depending on the circumstances.

IP addresses by daily volume

GreenArrow, a mail server vendor, sizes the number of sending IP addresses like this:

Too many addresses look like snowshoeing

Spammers use a technique called snowshoeing. They spread their volume thinly over a large number of IP addresses, so that no single address sends enough mail to draw attention. Mailbox providers know the pattern. When a sender uses many addresses for the amount of mail it sends, they penalize that sender.

If you have spread your mail over many addresses, and your complaint rate is very high or your engagement is low, read Two Worlds of Email Deliverability before you move your mail onto fewer addresses.

Too little mail on each address

Keep every IP address above 40,000 messages a week. Mailbox providers judge an address by the engagement and complaints its mail produces. Below that volume, they see too little mail for those numbers to be statistically significant.

That figure is the general floor for any address. A dedicated IP address for transactional mail can be justified at a lower volume, and each email service provider (ESP) sets its own minimum. The dedicated-IP volume floors table compares these figures.

Related articles

• Advanced IP Segmentation and Allocation
• IP Warm-Up