Can I create a lead from my email inbox without having to go into Zendesk?
It is not possible to automatically create a lead from your inbox without logging in to Zendesk. However, if you integrated your email with Zendesk Sell, you can see any sender who is not associated with a Sell lead or contact in Suggested people tab in the Communications Center. For more information, see this article: Adding suggested people as a lead or contact.
If you installed the Zendesk Sell app in Support, you can also create a lead in Sell from the ticket without having to open your Sell account.
Alternatively, there are other ways for you to bring leads into Sell. For example, you can leverage Google contacts and synchronize your contacts with Sell. For an exhaustive list of all the possibilities, see this article: Bringing leads into Sell from different sources.