When a notification, alert or confirmation message must be sent by email to the user, use plain text instead of HTML whenever possible.
A confirmation email confirming a request to be contacted does not justify HTML code and images.
A basic HTML message uses on average:
- at least 2 images (the logo and signature at the bototm), approximately 10 KB - 12 KB of HTML for the layout (inline styles, tables, etc.) - 4 KB of text (the message + 2 action links)
- HTML email = 26 KB - Plain text email = 4 KB
A saving of 22 KB for each email sent.
The potential saving for an e-commerce website with both customer and internal alerts could therefore be enormous.