Here's How I Mined My Mailbox to Find The Top Email Service Providers

Using IMAP, I was curious about what email service top apps use; being particularly interested in transactional email services. Is there a way I can go through my mailbox, check product emails and check the service for each? Sounds like a fun experiment to give a shot. I decided to pull all the emails instead of pulling them from a Yahoo mail dedicated to product signups, subscriptions and newsletters. After reviewing a couple of headers in Yahoo mail, I found a pattern to match the provider.