Exchange 2016 Maximum number of recipients in a message that's sent by the specific sender

In Exchange 2016, the RecipientLimits property on a mailbox takes precedence over the organization-wide MaxRecipientEnvelopeLimit. That means if you set the global MaxRecipientEnvelopeLimit to 50 but configure a specific mailbox (e.g., user10@mylab.local
) with RecipientLimits set to Unlimited, that mailbox can bypass the organizational limit. In your example, user10 would indeed be able to send a message to 100 recipients, since the mailbox-specific RecipientLimits overrides the global setting.