First of all, kudos to the ZippySig team on the very smart SEO approach. Nicely done!
I manage several brands and niche sites, all associated one way or another with the Heaviside Group brand. Some are obvious, like our niche agency. Some are not, such as niche sites we monetize via various methods that you would not even know are connected with HG. In order to do that properly, I personally manage many email addresses.
We do this by funneling all of them into my main Office 365 email account. I've set it up so I can send and receive all of those email accounts from that account. That solves one problem while creating another: how can I differentiate each email signature without having to type in a lame one each time, and maintaining a professional signature appearance.
While poking around Google I found ZippySig. It's the perfect solution to this problem. It allows you to create customized email signatures that look great very quickly. There are several templates you can work from that will accommodate most signature types you can think of. Once you're done, they provide instructions on how to integrate the signature into your email client. This allows me to generate custom signatures for each niche site I manage and store them in a single location.
There is a free trial that will let you try it out, and the plans are reasonable a reasonable cost after that. Great product!