You have a recommendation and two people who have to live with it. The easy mistake is to write as if the software can sit them down together. It cannot. One briefing goes to one mailbox. The person who opens it is the one who has to walk it across the room, or not.
This is not a plan. It is a decision request one partner can forward in their own words without translating you.
Write for the partner who was not in the last meeting
Assume the reader missed the call. Give the current position, the two or three options that are still open, and what each option spends — time, cash they will not have for something else, a door that closes. Then your lean, and the fact that would flip it.
Do not recap the whole relationship. They hired you for that. They are being asked to choose a next step. If answering well means opening a packet, you assigned homework. RelayLink does not carry attachments. Describe the statement or the illustration: which account, which figure, which date it was as-of.
A couple will often reply "we need to talk." That is fine if the talk has a closed list. It is a stall if the list was never written.
One mailbox is a fact, not a slight
Address the person whose inbox you are using, and say plainly that the other person needs to see the same choice before you treat a reply as theirs. If you have two addresses, send two briefings with the same ask, or send one and let them carry it. Do not invent a group.
Writing to someone who is not on RelayLink is ordinary here. Many clients have never activated an account. They get email and a link. If one of them already has an activated account and the other does not, the doors are different: cold email to the unclaimed address, an accepted pair before a new thread with the person who already signed in. The refusal will not tell you which.
A nickname you use for "the house" or one partner stays on your side. The briefing uses names they would recognise.
The reply is the decision
The reply is the point. You approve the wording before it leaves. They can answer from the email. A sufficient reply is which option, and whether both of them have seen it. If only one has, say what you will hold until the other has.
Mark the premises they can correct: that they still want the date you named, that the cash figure you are using is the one they recognise, that neither of them has already decided in a hallway you were not in. An assistant will fill those gaps with confidence. Label the fill.
What you are not doing in this message
You are not asking them to become analysts. You are not asking them to approve a theory your assistant built from a partial file. You are asking them to own a choice in a form you can act on.
If they need a meeting, ask for the meeting as its own request, with the same closed list in the invite. The briefing still goes first, so the meeting is about the disagreement, not about finding the question.