Email HTML Signature Going To Junk Mail

Good afternoon.
I have had an email signature created some time ago and it was revised recently.
For some reason since this, our emails largely seem to be filtered into peoples junk/spam folders.

I wanted to engage with the services of an expert in this field who knows how to work on HTML signatures which will not going into junk folders.

I believe there are certain parameters which will when creating a HTML signature the code should adopt in order to avoid this being the case.

If you are an expert in this field and can do this for me please reach out.

We are happy with our current signature so it may just need some tweeking on the code.

Thanks.