Sharing emails with a third party can be a tricky legal issue. Depending on the nature of the email and the purpose of the third party, it can be legal under certain circumstances. For example, if you are sharing an email with a lawyer or a legal advisor, this is usually considered legal. However, if you are sharing emails with a third party for commercial or marketing purposes, then it may not be legal without prior permission from the sender. It is important to check the terms of service and local laws before sharing any emails with a third party.