Many people now are using Smartphones, which have limited screen area for viewing messages.
Also, many people don't have a lot of time available for reading, or don't like to read. If you don't write what's essential in the first sentence or two, they won't see it.
Whenever possible, type your reply above any quoted message
Makes it immediately visible without scrolling.
Sometimes reponding in-line with the quoted message is necessary when many points have to be covered. If that's the case, state that's what you're doing.
Provide meaningful Subject lines
More likely to get an immediate response
Simplifies locating messages later
DON'T TYPE IN ALL CAPS
it's the equivalent of shouting and can be quite annoying.
Don't use an image as a signature
Causes maibox bloat both for you and your correspondent.
Avoid large attachments
Whenever possible, provide a link to a document on a Web server.
Many large attachments quickly add up -- eating up both your mail quota and that of the recipient.
Help Yourself
Minimize the volume of your stored email
Despite their convenience, Email servers, and Exchange in particular, are not designed to be efficient file storage systems.
Improves mail server response
Eases the finding of messages
Use folders to organize messages
Eases the finding of messages
Use a meaningful folder name, not a short, cryptic one
Delete unnecessary messages immediately; extract and delete large attachments.
Cornell's 7GB limit can't be expanded.
Don't procrastinate
If you put it off until your mailbox fills up, you'll spending many hours cleaning up your mailbox.
The sender will receive an error message if your mailbox is full, and will have to manually send the message again. As a result, you might not receive important messages in a timely fashion. If your correspondents don't resend them, you won't receive them at all.
Password protection
Don't share your NetID's password with anyone. In addition to your email, it provides access to your HR information.
Don't use the same password for non-Cornell services, so if one is compromised it doesn't jeopardize another.
Don't type it on public, non-Cornell computers. Keybord capture malware is much too common.
3rd-Party services (gmail, yahoo, etc)
Use 3rd party mail services for personal mail.
separate from work correspondence
reduces mailbox bloat
Don't use 3rd party mail services for Cornell business mail.
There usually is a lack of privacy, potentially exposing Cornell's business to inappropriate 4th parties.
e.g. Google scans email content in order to display topical advertisements.
There can be "legal discovery" issues.
When there is a workplace legal dispute, access to all work-related mail is required.
Lack of access can potentially result in a finding in favor of the complaintant.
The legal process for getting access to messages on 3rd party systems can be expensive and lengthy.