The instinct on adopting a channel that gets read is to move everything to it. That is the reliable way to stop it getting read. iMessage does one job better than anything else, and a handful of jobs worse.
The job it wins
Short, timely, personal, and expecting a response. A confirmation that needs a yes. An arrival window. A question that unblocks a job. A follow-up that should feel like a person wrote it. In every one of those, the immediacy and the reply affordance are doing the work.
The jobs it loses
| Job | Better channel | Why |
|---|---|---|
| Anything long | A quote, a report, terms. It needs to be findable later | |
| Anything needing an attachment they will keep | Invoices and warranties live in an inbox, not a thread | |
| Regular content | A newsletter in a message thread is an intrusion | |
| Anything to a list you bought | None | This is how lines get flagged, and it is unlawful |
| Reaching Android users richly | RCS | It is not a blue bubble and never will be |
| A decision needing comparison | Email or a page | People compare on a screen, not in a thread |
The pattern that works: message about, email the thing
Send the quote by email because it needs to be findable during a decision. Then send a short message saying it is there and what the headline is. The message gets read, the email gets kept, and neither is doing the other's job. This one pattern resolves most channel-mix questions.
A worked allocation
| Moment | Channel | Content |
|---|---|---|
| Enquiry received | iMessage | One question, within minutes |
| Quote ready | Email + iMessage | Document by email, headline by message |
| Quote follow-up | iMessage | A genuine question, not a nudge |
| Booking confirmed | iMessage | Window, technician, what to clear |
| Evening before | iMessage | Confirm, one-tap reschedule |
| On the way | iMessage | Name, ETA |
| Job complete | iMessage + email | Photos by message, invoice by email |
| Review request | iMessage | 90 minutes after close |
| Seasonal reminder | Not urgent, and it can be ignored politely | |
| Annual check-in | iMessage | Once. Referencing their actual job |
Nine messages across a whole relationship, most of them logistics the customer wants. The seasonal newsletter stays in email, where being ignored costs nothing.
The frequency ceiling
Email tolerates weekly. SMS tolerates less. iMessage tolerates least of all, because the thread sits next to messages from the customer's family and every one of yours is judged against that context.
A practical ceiling: one non-transactional message per customer per month, and as many transactional ones as the job genuinely requires. Transactional volume is almost never the problem; promotional volume almost always is.
And keep the fallback working. A channel mix where iMessage is one of three is resilient; one where it is the only path to a customer is a business risk regardless of how well it performs. The honest version of that risk.