Technically speaking, you are allowed to have
multiple IP addresses. However, you must justify the necessity for the multiple IP addresses. Do you have to deal with unusually large volumes of data within limited time frames? Do you need different IP addresses to segment them according to specific mail streams? Both these situations can easily justify the need for multiple IP addresses. Other factors the fuel the need for more than one IP address are volume of job, maintaining reputation of fast and hassle-free delivery, budget and other aspects that can lead to better and smooth management of key areas of your business.