We all are familiar with sending an email to ourselves to keep important things on top of the inbox. Say you are attending a webinar or web conference from outside US, since the webinar happens at the US time, it helps to know the exact time in your local time. You can get that information from TimeandDate.com Converter.
Once you have the information, hit the reply button of the webinar details email, change the sender to your email, to email yourself a copy of that mail. You can copy paste instead but reply and mailing yourself is quick, Now, to add time and other details to it, just reply to that mail with those information. This way adding notes to email is easier. You can do this to any mail. This way I find it easier to nest all the information I need in a single mail.
This works better if you email yourself with a mail address modifier like firstname.lastname@example.org, when your mail is email@example.com. Then creating a filter to that modified mail ID will keep your things organized in a file (label).