Any way to make email wrapper logo responsive?

[The Old Man]

Hi,

I updated my default email template to test it with a wider image than my usual logo, based on my community's background header image which is 1920px by 200px, but a separate version with the name of the site included in the image instead of it being a separate logo like the header arrangement. The standard one bugged me as it never filled the width of the email header.

I've tried setting the CSS to Background-size property to cover.

In the Gmail App it now shows roughly just the first third (the left part of rectangular image) and you have to scroll sideways left to see the rest of the image off-screen over to the right.

In the iOS Mail app however, it shows the whole full width image in the view, zoomed out so far, you can't read the actual text elements of the email.

The source code appears to be responsive, but it doesn't work consistently. Oddly the html email source code has an XHTML Doctype instead of HTML5 method.

Anyone noticed this before and been able to resolve it?

Many thanks.