CONFIRMED: Mixing transactional and promotional sends through one stream is the deliverability mistake nobody

CONFIRMED: Mixing transactional and promotional sends through one stream is the deliverability mistake nobody confesses to.

A receipt and a flash-sale email feel similar, but mailbox providers judge them differently. Slip a promo into your transactional stream and you risk dragging order confirmations into spam — the one email customers actually need.

What insiders enforce: hard separation. Different subdomains, different IPs, sometimes different vendors entirely.

— Keep order/password/receipt mail on a clean, low-volume domain
— Never upsell aggressively inside a transactional template

Watch this.