I've come across several threads on using subdomains for sending marketing emails, but they're several years old... So I thought I'd check in to see what's best practice these days.
Our IT team flagged that we have too many authorized servers in our MX record. Several are for normal corporate email, others for 3rd-party emailing systems such as Marketo. They continue to get requests from time to time from departments to add even more 3rd-party servers. They suggested subdomains (i.e. @x.company.com) be set up for the 3rd-party systems to prevent negatively impacting the "real" corporate email.
Is your company sending marketing emails from a different subdomain or not? What are the considerations/pros/cons? Does volume matter? Would we have to warm up the new subdomain like we did when we first started using Marketo?