How to Set Up an HTML Email Signature in Microsoft 365?

As an admin, you can use mail flow rules to apply signatures for all or specific users. There's an official Microsoft article that explains how to create signatures and disclaimers in Exchange. You could check that out for guidance if you want to enforce a signature. Though, an image will need to be hosted online for this approach.

If you want managed signatures, consider using a tool like Signitic. Otherwise, you can create a template and ask the users to set it up themselves. However, setting up HTML can be a pain, and if you're using Word to insert HTML, you're likely to run into problems because Word can mess it all up.

Setting up custom signatures for each user in Microsoft 365 has to be done individually if you want specific details like their names or roles. Unfortunately, there's no way to bulk configure those. As for images, they don't have to be hosted elsewhere if you're okay with using inline images that are attached to the message. Just a heads up though, you might face issues with images on iOS since AppleWebKit can mess up inline URIs, which might lead to broken links.

For a smoother experience, I suggest using Exclaimer. Seriously, trying to manage signatures in M365 can be a headache, and adding images just complicates things even more. Trust me, stick to text for simplicity. But if you insist on using an image, you will indeed need it to be hosted somewhere accessible.

I've had great results with CodeTwo. It's made things so much easier compared to using the default O365 tool. In fact, I highly recommend it if you can get approval. It really takes the stress out of signature management, which can be quite a hassle.