Basic IP Allocation

One big question that many people have when setting up a new email server is “how many IP addresses should I be using”.

Basic advice

This document also assumes that you have a single kind of email that you send and that there is no need to split out different kinds of email onto different IP addresses to maintain different reputations.

If your needs are more advanced, see the Advanced IP Segmentation and Allocation article.

What this document assumes

This document makes recommendation for maximizing deliverability of email that is wanted and expected email.

Deliverability of email that is not wanted and expected may actually suffer from following these recommendations, depending on the details.

Number of IP addresses

We recommend determining the number of IP addresses using the following chart:

Messages per day	Number of IPs
less than 40,000	One
between 40,000 and 200,000	Two
more than 200,000	Between 100,000 and 1,000,000 messages per IP address per day

Don’t use too many IP addresses

Spreading mail over too many IP addresses looks like a spamming technique called “snowshoeing.” Snowshoeing spreads a volume of mail over a lot of different IP addresses with the idea that each IP address can fly “under the radar” by having only a very small volume on each IP address. The problem with this is that the ISPs are aware of this technique and penalize senders when they see mail coming from too many IP addresses relative to the volume.

If you have been snowshoeing and are sending email with a very high complaint ratio or a low engagement ratio, then you should read the document Two Worlds of Email Deliverability before changing to use a smaller number of IP addresses.

Have enough volume on each IP

We recommend that a single IP Address not send less than 40,000 messages in a week.

This is because you need to send enough email from an IP address so that the ISPs get enough engagement and complaint information on your email to be statistically significant.