WiseStamp - WiseStamp allows you to easily create and implement slick and unique email signatures for your business.
Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.
MySignature - MySignature is FREE Email Signature Generator that helps to create Professional Signatures for major email clients such as Outlook, Gmail...
Hiver - Manage Customer Support, Sales and Projects right from your Gmail inbox. Collaborate with Shared Labels, Shared Contacts, email notes, email reminders and email templates
Sigstr - Email signature marketing
MailClark - The Slack bot for external communications