Spacer.gif in e-mail

Spacer.gif in e-mail

When answering a ticket by e-mail, a 1x1 image 'spacer.gif' is placed into the e-mail. When a customer wants to answer this e-mail but doesn't allow external content to be in the e-mail, the e-mail gets a weird format. (see image below)


Is there a possibility to remove this 1x1 image when sending an e-mail from Zoho Desk?