Plain text.

Images bug the hell out of me because all my emails show as having attachments in my inbox then and when you forward them to Trello they attach the signatures to cards.

Just plain text. Gmail.

We make an html file with our logo and links that we can copy and paste into our mail app. It works, but not ideal.

We host any images internally. Create some basic html, spin it up as a webpage and host it internally, and then we have a link to it in our internal training docs that employees can copy and paste into Gmail signatures. We update the HTML file anytime it needs to be adjusted and send out a company-wide email when we want employees to re-update their signatures.

There are a handful of email signature Saas companies out there if you just google them.

We use Sigstr for our email signatures. It's a great service that allows one person to customize the images that appear in the signature of our whole companies email. It's really really nice.

https://www.sigstr.com/

Has anyone else encountered problems recently with signatures causing the mail to get caught in spam filters? It's been a real problem in the last couple of months - even for a mail server that has DKIM and SPF...

I used to have a fancy HTML signature, then moved to an image only and now just formatted text. The HTML version is such a pain and there are so many different clients to test for that it's almost impossible to get it working exactly how you want it for everyone. There are templates and tools like Litmus you can use to test, and there are pros who specialise on that on Upwork, but it's simpler to just find a compromise and use an image or plain text, it's gonna work in every client on any platform and you'll save yourself a lot of pain.

HTML without images.

It's really the only way to be compatible with Outlook.