SMTP relays
How we keep deliverability up with SMTP relays
One of the ways we make sure your email is delivered properly is by watching and controlling our sending relays closely.
Spread across several relays
A sending relay is a group of individual SMTP servers serving one purpose. We use different relays depending on what is being delivered.
Sending is spread across the individual servers by an algorithm we built ourselves. It keeps the load even and tunes the delivery speed to the receiving systems.
The system keeps learning which speed each receiving system prefers, from both technical and manual feedback. We also maintain databases of invalid domains, addresses and spam traps that must not be delivered to.
Watched through outside sources
We pull data daily from external reputation databases about our deliveries. That lets us catch a problem on a single server in our SMTP cluster before it spreads.
Among the sources we watch:
- Google Postmaster Tools
- Outlook.com: Smart Network Data Services
- Validity: SenderScore
- Cisco: IronPort SenderBase
- More than 200 real-time blackhole lists
Reporting per domain
Every server in the cluster reports weekly on delivery speed and on any delays caused by blocking. It happens per domain, so we can see quickly where a problem sits.
When we find one, it can usually be solved by tuning the configuration, which puts the speed back where it belongs.
We watch for what stands out
When a newsletter leaves our systems it joins our overall statistics. Those let us find sends that behave differently from the rest.
We follow open rate, click rate, bounce rate and spam rate, among others. It lets us spot misuse quickly, before it costs everyone else their deliverability.
Want to know more about deliverability?
We are happy to walk through how your sending arrives.