This is the easiest and quickest option as users can modify their signatures themselves.

You can provide your users with a prototype signature file on a periodic basis and ask them to update via Outlook/OWA. It is possible to set up Outlook so that signatures are automatically added to all outgoing messages or create your signature and add it to messages on a case-by-case basis. Your signature can include text, images, your electronic business card, a logo, or even an image of your handwritten signature.

In Outlook, you can create one or more personalized signatures for your email messages. There are a few ways to set up a signature in Microsoft 365: Manually create and add a signature to your messages Managing email signatures for your entire company can be challenging but with Microsoft 365 or Office 365 you can easily create organization-wide email signatures and disclaimers. Email signatures contain essential information and can brand every new email you send as you correspond with your clients, vendors, and prospects.

How to add a logo to your email signature outlook