[gwittel]

Yes. In the past I helped sort out tooling like this for competitive analysts. There are a few ways this is done:

1) Check the businesses’ MX record. Often this points to a third party provider like Microsoft or Google. 2) Connect to the mail server identified in the MX record. Sometimes these have banners that identify the vendor (vs something generic like sendmail) 3) Email headers from messages sent to users in the company (or sometimes a bounce). Often these have headers from one or more providers. You’ll have to sort out the path to understand which bits were added by the sender/recipient path though.

These days often companies have multiple providers (security) so they might have one at the edge (mx) and more internal hops. You can usually see these in the headers.