Grouping ips into pools
If you have several ips you might want to consider grouping them. This helps getting a good average deliverability.
Every big sender has different customers. Some are premium (clean lists, good content), some are close to spammers. So you create a good pool (A) and a medium pool (B) and a pool (C). Good senders go into A, most of the senders go to B and the difficult customers go into C. That has the advantage, that a bad send-out (horrible list or very bad content) of a C rated customer doesn't hurt the next send-out of a good customer. Plus, if you get a new customer who the company wants to have at all costs, you put him in the A pool for the test send-out and everything will go well. It will happen, that your boss wants to take a potential customer you don't want to have...put him in C and if he spams it is not a problem.