I was excited to see that my team's work for T-Mobile received kudos in this blog post from MyEmma.com https://content.myemma.com/blog/email-showdown-verizon-vs-at-t-vs-t-mobile

However, I was shocked to see the screenshot of our preheaders in Gmail which showed HTML in the preheader. We do a very thorough job of checking our campaigns so I wanted to see if I could recreate this.

Our email preheaders look good in the Gmail inbox

But when you search the inbox, the same email now shows HTML in the preheader

I think what happens is the preheader displays the first instance of the string searched for and then displays the code leading up to and/or after that string.

Has anyone else noticed this? Any ideas on how to prevent it?