WiseStamp - WiseStamp allows you to easily create and implement slick and unique email signatures for your business.
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
MySignature - MySignature is FREE Email Signature Generator that helps to create Professional Signatures for major email clients such as Outlook, Gmail...
Brevo - Innovative online Email Marketing solution to manage your contacts, create & send your newsletters and track your results. More than 80 000 clients. Best prices and attractive features.
Sigstr - Email signature marketing
Campaign Monitor - Email marketing software built for designers and their clients to run successful email campaigns.