Disabling automatic inline CSS
For the longest time the advice was to not use style in the head tag of your HTML emails due to the lack of support in a vast majority of email clients. It was always recommended to use inline CSS using the style attribute on each HTML tag.
SendCastle always automatically did all this for you. That is, if you had styles defined in style tags, we would move it to inline attributes for you.
These days the support for style tags are slowly getting better and better, therefore we have now added the option to disable this conversion in SendCastle. This is aimed at more advanced usage where you want full control over the styling of the email.
You can disable automatic inline CSS conversion on individual segments by going to the segment settings (this is done by zooming in on the segment, then clicking its title).
If SendCastle's automatic inline CSS conversion never bothered you, you should probably leave the option to its default (that is off, or unchecked).
Note that in order to send responsive emails, you do not need to disable inline CSS conversion, we leave any media queries intact -- the default behaviour should work fine for you.