Email / domain reputation is very complex. Their domain may have been flagged due to excessive marketing emails, so no matter what they send they are heavily weighted towards spam.
I worked at a SaaS company that had about 50 sales reps. They were sending emails day and night, eventually getting the main corporate domain flagged. The product's transactional emails (signup, confirmation, etc.) would be flagged as spam, until we moved them to their own domain.
I worked at a SaaS company that had about 50 sales reps. They were sending emails day and night, eventually getting the main corporate domain flagged. The product's transactional emails (signup, confirmation, etc.) would be flagged as spam, until we moved them to their own domain.