If a submissive contacts me with a friendly email and it’s clear (or becomes clear) that they are partnered, I don’t go and ask their dominant if it’s okay that we interact (not flirting, not arranging a hookup, just having friendly conversation). I assume that we are all adults and they can make their own decisions. It’s not my job to police other people’s relationships.
So if I’m corresponding with a submissive and I get an email from their partner that says something akin to ‘WTF?! HAVE YOU NO RESPECT?!’ my response is going to be bafflement that whatever problem they have with their own boundaries has somehow become MY issue instead of an issue between them.
Seriously: it’s nothing to do with me.
My reaction is going to be to block both of them.
Because ‘get your idiotic melodrama the hell out of my inbox, both of you!’