What are the trade-offs of using operational emails?

Operational emails reach prospects who have opted out of marketing communications, which is exactly right for receipts, service notices, event logistics, and password resets. Note that they still do not reach prospects flagged 'Do Not Email'.

The trade-off is that the flag is trivially easy to misuse. Marking a promotional email operational to increase reach is a compliance problem under regulations such as GDPR and CAN-SPAM, and it is a trust problem with recipients who explicitly asked to stop hearing from you. It also corrupts your reporting, because opt-out rates stop reflecting reality.

My rule is a simple test: could the recipient reasonably regard this message as something they need in order to use a product or service they already have? If not, it is marketing, whatever the subject line says. I would also make the setting a review item so it cannot be flipped without someone noticing.