IP pools allow you to group your dedicated SendGrid IP addresses. For example, you could create separate one pool for your transactional email and another for your marketing email. When sending marketing emails, specify that you want to use the marketing IP pool. This allows you to maintain separate reputations for your different email traffic.
A single IP address or a range of IP addresses may be dedicated to an account in order to send email for multiple domains. The reputation of this IP is determined by the aggregate performance of all email traffic sent from it.
IP pools can only be used with IP addresses for which you've set up a reverse DNS record.
If an IP pool is not specified for an email, it will use any IP available, including pooled addresses.
Each user can create up to 100 different IP pools.