Email, Messaging, & Video Calls Email How to Show Message Sizes in Apple Mail Keep an eye on your storage by Heinz Tschabitscher Writer A former freelance contributor who has reviewed hundreds of email programs and services since 1997. our editorial process Heinz Tschabitscher Updated on October 14, 2020 Email Yahoo! Mail Gmail Tweet Share Email Most email messages are small. Some have a reported size of 0 bytes, but exceptions exist. To spot larger messages immediately at once when you look at a mailbox in Apple's Mail app, you can include the message size in the list of displayed message attributes. Instructions in this article apply to Mac OS X 10.11 and higher. How to Show Message Sizes in Apple Mail To display the message size in the Mail message list: Go to your inbox in the Mail app and select View on the menu bar. Select Show Message Size in the drop-down menu. Now, the size of a message appears under the date you received it. If you want to sort your email by size, select Sort By in the View menu and choose Size. Why Would You Want to Know the Message Size? You might want to know the message size to determine whether a message has attachments or images in it. You might be looking for an especially long message or one with a lot of information or a large attachment. If your mailbox is full, you may want to delete large messages first to free up space on the mail server or to speed up the syncing of a new device.