We have a commitment to all of our customers that their good sending practices will be used to enhance their own deliverability — not to build up the reputation of someone else. It’s not a respectable practice to use other customers to warmup an IP.
Even while pre-warmed IPs offer a quick start to higher volume sending, receivers quickly catch on that the IP has changed hands and adjust the reputation accordingly. Despite what another provider may say, pre-warmed IPs are nothing but a temporary solution.
If you’d like to send higher volume from the start, we recommend using our managed warmup process or even just testing all your messages in our shared IP pool. Many senders find that Postmark’s high-quality shared traffic actually improves their deliverability, rather than isolating themselves on a dedicated IP.