This is certainly great. But, like mixing work and play, packing too many different subjects into one message can make things pretty confusing.
Talk About One Subject per Email Message Only
This is why it is a good idea to
- start a new message when you start writing about a new subject.
The new subject is also reflected in the Subject: header field of the new message and it makes organizing mail a lot easier when you know from the Subject what to expect in a message.
What About Emails to Friends?
Of course, this is not a rule that is always applicable. If you are writing an email letter to a friend or family member — and the point of a letter may well be that you are jumping from one subject to the next and back again, then start anew somewhere completely different —, forget about it. But if you're about to hide an important piece of information that your friend needs to act on or reply to swiftly, remember it again and send a separate email with that information quickly.

