Email marketing startup Sendwithus is announcing that it has raised $2.3 million in additional seed funding.

This is one of those funding announcements that comes months after the deal itself. Co-founder Matt Harris told me that the company, which was incubated by Y Combinator, raised its initial seed funding “right before Y Combinator started”, then raised additional funding on demo day in March.

The Sendwithus team wanted to announce the funding now, in part, to highlight its new features and the success it has seen so far. When I wrote about the company earlier this year, it offered tools like A/B testing to optimize transactional emails — i.e., emails for specific purposes and tied to specific events, such as “reset your password” and “thanks for signing up!” (The service integrates with email delivery services like SendGrid and Mailgun.)

Harris admitted that focusing on transactional emails sounds “super boring.” However, every company sends them, customers are more likely to open them, and they’re messages that “most marketers don’t get access to and don’t even think about.” Sendwithus allows marketers to test different variations of those messages without having to go through a developer. He also said that at larger companies, sending these emails “becomes a real pain to manage, produce, and automate … so what we’re effectively doing is productizing those systems better than these companies would ever do themselves.”

More recently, Sendwithus has added segmentation capabilities, allowing businesses to drill down on specific groups in their customer database — for example users who received an activation email but didn’t activate.

“The end result is that with very little effort, this company is able to send really personalized email to a specific segment of customers,” Harris said.

Apparently the company has been seeing 30 percent monthly revenue growth for the past eight months, and the product has been used to optimize 250 million emails.

The funding, meanwhile, was led by Steve Anderson of Baseline Ventures, with participation from SV Angel, Maiden Lane, Garry Tan, Alexis Ohanian, Paul Buchheit, Kevin Hale (Tan, Ohanian, Buchheit, and Hale are all partners at YC), Scott Banister, and others. Sendiwthus has now raised a total of $2.6 million.

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