Delivering Millions of Electronic Signatures with Transactional Email

Written by Mailgun Team

Categories: Case Studies

3 minute read time

About SIGNiX

In the E-signature space, SIGNiX creates a great user experience by bringing security and ease of use to its digital signature platform. Their software solution helps over 700k customers manage contracts and important documents in a timely manner. Most of these customers operate in highly regulated industries like wealth management, financial services, banking, healthcare, pharmaceuticals, government, and real estate. SIGNiX relies on sending transactional email through Mailgun to let recipients know in real-time that their documents are ready for signature.


To keep pace with the growth of their SaaS platform, SIGNiX was looking for a way to scale and send their email messages at a higher volume. The team at SIGNiX knew they needed help from an email service provider that had experience sending a lot of emails; one that could help them transition away from sending SMTP email in-house. It was becoming more complicated to send over 4 million emails every month and maintain a good sending reputation along the way, especially with their increase in inbound messages. A higher volume of messages was coming from new customers who signed up for the platform and sent out contracts for the first time. This had a big effect on the health of SIGNiX’s sending domains and dedicated IPs.

Each new customer triggers emails that need to be sent through the platform anytime they generate a new contract. With very little control over a customer’s sending needs, SIGNiX had to find a way to manage sending all of those emails 24/7. They also wanted access to email analytics that would let them see delivery rates, bounce rates, suppressions, and other performance metrics to track what happens after those messages were sent out.

“Deliverability and consistency are critically important when email is used as the primary notification mechanism for our digital signature service. If the emails don’t go out, it’s difficult for new buyers to sign off on that contract for their beautiful new house…”

Anthony Sims, Marketing Director


With help from Mailgun and a dedicated Technical Account Manager, SIGNiX was able to improve the reputation of the dedicated IPs their team uses to send transactional email. Together, they developed a sending schedule for each new IP to slowly increase the volume of messages being sent. During this IP warm-up process, they were able to fall back on shared IPs to continue sending out extra messages that didn’t fit within the sending schedule. This helped SIGNiX improve their sending reputation and reduce the throttling they had seen before with an ISP that had previously greylisted their domains.

Aside from their improved deliverability, SigniX was also able to create robust reporting for their customer base and suppressions with Mailgun’s Analytics tool. That way, they can notify their users right away with push notifications when messages don’t deliver and provide options to get their documents signed.

“Email deliverability is huge for SIGNiX. Without these emails being delivered in a timely and reliable manner, we would struggle to keep our customers happy.”

Anthony Sims, Marketing Director


By following the IP warm up process, SIGNiX was able to increase the volume of email messages sent, and they have achieved a delivery rate of over 99%. Their IPs and domains have improved, and they maintain a consistently high reputation with leading ISPs like Google.

“We’ve always been happy with our relationship with Mailgun. It gives us peace of mind.”

John Harris, CTO

About Mailgun

A Y-Combinator success story, Mailgun is an email delivery engine created by developers for developers. Since 2010, Mailgun has provided deliverability expertise and leading technology via cloud-based email APIs for customers such as Slack, Github, and Shopify. Through its own proprietary technology, Mailgun strives to continuously ensure you can send, receive, and track email effortlessly.

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Modified on: February 21, 2019

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