Understanding Email Headers

Gmail has many automatic systems to protect its users from spam and malicious attachments, but it goes even further: Gmail can mark an email as important, change the ways it displays headers, and sort incoming emails into categories to keep your Primary inbox as clutter-free as possible.

Importance marker

Within your inbox, importance markers are the right-facing arrows on each email between the star and the sender’s name. A yellow importance marker means important, no color means unimportant. Gmail uses several signals to decide which messages to automatically mark as important, including the following list from Google help:

• Who you email, and how often you email them.
• Which emails you open.
• Which emails you reply to.
• Keywords that are in emails you usually read.
• Which emails you star , archive , or send to trash.

Hover over any yellow importance marker to see why the email was marked as important. Click an importance marker to change it. Doing this teaches Gmail what messages you think are important and which are not.

To view only emails that are marked as important, click Important in the label list or search Gmail for “is:important.”

Personal level indicator

Personal level indicators display within the importance marker. These small chevrons indicate whether the email was sent only to you or to a group.

• Two chevrons  . Indicates the email was sent to you only.
• One chevron . Indicates the email was sent to you and others.
• No chevron . Indicates Gmail cannot tell if it was sent to others or not. This likely means the email was sent to a mailing list, and all recipients were placed in the BCC: (blind carbon copy) line instead of the To: line, as is often the case with a newsletter. BCC recipients can only see the email and who sent it.

Email Headers

When you open an email, the top portion of the email (the header) contains important information about the sender, whether it was sent just to you or a group of people, the date and time it was sent, and other information. Let’s look at a random marketing email as an example.

The top line contains:

• The subject of the email.
• The importance marker. Note that the personal level indicators (the chevrons within the importance marker) do not appear in the header of an email, only in the inbox list.
• Label(s). “Inbox” is the only label in our example.
• Commands. You can print the email or ‘pop it out’ into its own window.

The next line contains:

• The sender. The sender’s user name is in bold, followed by the actual email address the email was sent from. The originating email address is important; anyone can use whatever user name they want, but email addresses cannot be spoofed or faked. Businesses will not misspell their business name, nor use random letters and numbers in the email address domain (the domain is the portion after the @ symbol). Real businesses will also have an “Unsubscribe” link next to their email address.
  • Gmail will hide the email address in emails from people in your contact list that you communicate with often, only displaying their user name.
• The receiver(s). If the email was only sent to you, “to me” will display, and if it was sent to multiple people, Gmail will try to display the names of all the recipients. If there are too many recipients, Gmail will display a number instead. Click the down arrow next to this to see all email addresses.
• The date and time the email was received.
• A toggle for marking the email with a star .
• The reply button.
• More commands (three stacked dots).