Note: This post is part of a special holiday blog series created by our Expert Services Team at SendGrid to provide information on how to prepare and get the most out of your email campaigns this year. “How many IPs should I have?” is a pretty common question we get from our senders. The answer is usually something like, “It depends.” Here’s a quick look into what you should be thinking about when deciding how many IPs you should have to support your sending needs. This is especially important to keep in mind as we head into the busy holiday sending season. Assess the considerations below to determine if you need additional IPs. Email Volume Generally speaking, the number of IPs a sender should use is directly correlated with their sending volume.The more messages you send per day, the more IPs you should have. The reason you need more IPs for more sending volume is because inbox providers have limits on the number of connections a single IP can make to their mail servers. They also have limits on how many messages can be sent across a single connection. Having more IP addresses allows you to open up more connections and thus send mail more quickly. Inbox Provider It is important to know that every inbox provider has different limits for the number of connections and the number of messages you can send across each connection. For example, Gmail pretty much accepts mail as fast as anyone can send it. Their infrastructure can handle extremely high volumes of mail in a very short period of time. On the other end of the spectrum are domains like orange.fr, wanadoo.fr, and t-online.de. These domains accept mail very slowly. If your audience is made up of a high percentage of wanadoo.fr recipients, you should probably have more IPs than someone who sends primarily to gmail.com recipients. Sending Reputation Similarly, your reputation can impact the rate at which you can send mail to certain email providers. A sender with a pristine sending reputation needs fewer IPs to deliver their mail than someone who generates a lot of spam reports or has poor engagement. Email Content The type of mail you send also matters. Transactional senders typically need fewer IPs than marketing senders because true transactional messages are spread throughout the day. Sending mail in large batches (which is more common with marketing email) can cause connection and throughput bottlenecks that necessitate more IPs. The truth is, there is no single answer for “how many IPs should I have?” because it really depends on a wide range of factors. However, with this information and SendGrid’s IP warmup and IP allocation guide, the vast majority of senders should have no problem figuring out how many IPs they need to support their sending.