You've posted this in Skype for Business but asked about Teams - so I'll give you the answer specific to Teams. What do you mean by "connect"? Do you mean have users in a single Team who are part of different Exchange organisations? And do you actually have multiple Exchange organisations, or just multiple servers? As you've mentioned both there. Ultimately it comes down to how it's all architected. You can have multiple Exchange servers connecting with Office 365 and therefore Teams - as long as a hybrid is established to the organisation. You can't have multiple Exchange organisations connecting to the same Office 365 at the same time. Also: Teams works best when the mailboxes are hosted in Exchange Online. There are specific compatibility constraints when using Exchange on-prem (or hosted outside of O365). I would suggest you review the session from Microsoft Ignite 2017 around Teams infrastructure and architecture as they cover this off.