Email signatures are those bits of text below the closing of a message and the name of the sender. They can be pretty crazy, or non-existent (which is worse). I've seen misspellings and other indicators of ineptitude. One of the worst types of infractions is when lawyers are involved, and legal disclaimers are appended to each and every message.
Email Signature Best Practices
The best email signature best practices are the simplest, because of the increasing use of mobile and cross-platform devices, images turned off by default (as well as HTML), and a degraded copy first approach.
Just as there is a greeting in many/most emails, there should be a closing, followed by a comma. For example:
Sincerely is a nice closing, it is short and sweet.
Two minus signs (hyphens)
Then after the closing, there should be a hard-return, and next comes the indicator of the signature, which is two hyphens (minus signs, or single vertical lines (sometimes called a dash).
Name (and possibly position)
Next after another hard-return, comes the name of the individual (or if anonymous, this can be omitted. For an individual who wants to include their title, it can be displayed after their name, such as Mr. Firstname Lastname, CEO.
Company or Organizational Unit
Next, after another hard-return (or hard line break in HTML) the organization or organizational element, such as Company X Customer Service.
Email or URL
While the email normally has the email address of the sender, it is nice (if a message is forwarded quite a bit) to have the email address of the sender in the message. If all emails generally go to one mailbox, or all mailboxes are listed clearly on the website under the Contact Us page, then instead of having the email address, include only the URL of the organization (or individual).
It is useful to have a phone number if people expect to use the phone. This can be excluded if dealing with a common phone number posted on the website.
Some Example Email Signatures
For a company department:
Company X Customer Service
+1 999 777-6666
For an individual:
Mr. Firstname Lastname - CEO, Company X
+1 999 888-7777
Article revised 19-feb-2016, originally published 23-sep-2013