Note sent-would marriage discussions and diplomatic discussions work well via a thread? Might keep it open and provide more room for negotiation
The whole point is that other countries wouldn't be privy to diplomatic/marriage negotiations they were not part of. Nothing stops someone who wants to contact everyone from sending out a message to every player's email at once, such as a player who has the only marriagable daughter announcing that they will now be entertaining offers for their daughter's hand in marriage, and someone who wanted open competition for such a situation could insist that a copy of all such offers be sent to the other interested parties.
But allowing secret negotiations really drives home the fact that the only diplomatic promises you can truly trust are those secured by marriage.
When negotiations for marriage contracts are complete, both parties will need to email me a copy of the contract. Both copies received need to be identical, or I will forward them to the other party with an indication that the contracts were not in agreement and further negotiations are apparently necessary. In such cases, I will extend the submission deadline for that phase slightly to allow hasty completion of any necessary corrections/renegotiations and resubmission of contracts from both parties. After all, since turns are 5 years long, the actual parties involved have lots of time in game to smooth out any contract discrepancies, but we don't want the game to bog down completely every time marriages roll around in the turn sequence.
As for exactly how long each segment of the turn will last, I plan on working out those details with the players so that the game will pulse at the speed they prefer. Hopefully this will allow everyone the time they need to complete their decisions without resulting in too much frustration over delays.