This is a very wrong approach

[Sneffel]

.preheader { color: transparent; display: none; height: 0; max-height: 0; max-width: 0; opacity: 0; overflow: hidden; mso-hide: all; visibility: hidden; width: 0; }

this, or the fact that it's all wrapped in an old td, tr table.

font-size: 16px;

This is so wrong

Please! Don't use this

[eulmdev]

a lot of email clients have terrible modern html/css standards and an older syntax is very good for compatibility