ISP's recommend you segment your marketing and transactional emails by using different IPs. I want to start using DKIM, but since DKIM is a domain based reputation system I wonder if signing with the same company.com domain will impact the reputation of transactional emails, since both them and marketing will be signed with the same domain? Is using DKIM with subdomains possible? Would something like this: bulk.company.com and transactional.company.com be a good idea? Thanks!