Originally Posted by PolyBrandy
I am not sure how to support him other than to tell him I love him.
Since you know your husband and we don't, I wouldn't think any of us anonymous people here on a message board can really tell you how to support him in this instance. The fact that the loss he's feeling is related to poly doesn't really change how you can be compassionate and supportive to your husband in the ways you usually are. You're the one who knows what cheers him up, what annoys him, how to be there for him, and what kind of space he needs if he wants to be alone, things like that. If you're still not sure, then ask him, as others here have said.
Edit: I just re-read your intro thread and am just wondering if perhaps you both got your hopes up about this person way too soon. You posted only a few days ago
to say you are both new to this and he'd just started messaging with someone. Perhaps it was a bit premature to think of this person as a "mate." Next time you two might want to move a little more slowly and cautiously.