Some customers don't use the Gmail app to read their email on mobile. They use the Safari browser.
Rendering of the newsletter is not so good. Is the media queries doese't work on the mobile Safari browser?

Simple example: the font-size must be smaller on smartphone devices:

@media only screen and (min-device-width : 320px) and (max-device-width : 480px) {
.text_mobile a {
font-size: 100px!important;
line-height: 100px!important;

How can I fix this?

Kind regards,