With the Office 365 native solutions, one should have a surplus knowledge of Transport Rules and HTML coding for the email signature to implement. There are various limitations users may face while designing the perfect email signature.
Various limitations for manually setting up Office 365 signatures:
•No email signature will be appended on reply emails
• No provision to test email signatures before implementing to all users.
• Can’t possible to embed images like logos or promotional banners in your email signature.
• No support for email signature sent mobile devices and Macs.
• Require perfect knowledge of HTML code.
•Can’t add email signature to Sent Items folder.

Sigsync Office 365 email signature service

Sigsync is a secured, centralized Office 365 signature service that helps to create and manage email signatures for all Office 365 users in your organization seamlessly. It appends signatures to all sent emails as well. It supports for the signatures to add for the emails sent from any device, including smartphones and tablets etc. The solution allows adding particular email signature elements including social media icons, promotional banners and legal disclaimers from centralized dashboard.
Key benefits:
• Supports Email signatures added to emails across all mail clients and devices
• Appends the signature for all the reply and forward emails
• Adds signature to the sent items folder
• Supports to signature to a particular recipient
• Provides preview of the signature during email compose in Outlook
• Supports OneClick survey and Web analytics
• Ensures high security using secure TLS channels and supports Multi-Factor Authentication(MFA) as an additional security

For More Information: Centrally Managed Office 365 Email Signature