No, unfortunately, most mainstream email services, including Gmail and Outlook, do not provide end-to-end encryption. They use the standard Transport Layer Security (TLS), which is the bare encryption minimum. This means your emails are encrypted while traveling, but they are stored in regular text, so third parties, including your ISP, can read them. Although Google claims it doesn't read your emails, you may have already experienced notifications that show otherwise, or events from your private mail casually placed in your calendar. Besides, most mainstream email services include various mail-reading permissions, most of which are very easy to give to third parties accidentally.