Email Delivery

What is Time to Inbox?

Time to Inbox is the length of time it takes from when an email is sent from a client until it shows up in the user’s inbox and is available to read.

Where does the Time to Inbox data come from?

Time to Inbox data is refreshed every 5 minutes. We generate the TTI (Time to Inbox) data internally using an automated system powered primarily by our MailHandler gem, which we recently released under an MIT license. Every five minutes, we send an email with consistent content to each of the five major ISPs (Gmail, Yahoo, Outlook/Hotmail, AOL, and iCloud/ Then we login to each service to check and see if it has arrived. Once it has arrived, we compare the time that it was sent to the time that we found it in the inbox and record how long it took to arrive.

This approach gives us the closest estimation of reality possible for end users and avoids skewing the numbers in our favour. We feel it’s best if our reported times match the true experience of a person checking their email.

What is the Inbox Rate?

When emails are sent, they’re classified one of three ways to determine the inbox rate. “Reached inbox” means that that the email was in the inbox. “Filtered as SPAM” means that the email was delivered but that it was found in the to the user’s spam folder. And “Lost during delivery” means that no record of the email was found. The percentage of emails that reached the inbox is the Inbox Rate.

Where does the Inbox Rate data come from?

Our Inbox Rate data comes from 250ok, a third-party provider in monitoring sending and reputation for legitimate email providers, and it is refreshed every 12 hours.

The Inbox Rate shows 100% delivered. Can I trust that?

Yes. Even though the data shows 100%, it is still accurate. We understand that it can be hard to believe, but we work really hard on this stuff. We’re not perfect, but blips on that 100% Inbox Rate are going to be few and far between. Rest assured that it’s working, and the data will show if we’re not on top of our game. These numbers represent our average inbox rate across all of our shared IPs (not just the best ones), using good content, and authentication like DKIM, SPF, and DMARC. The Inbox Rate is updated every 12 hours and is only for the domains shown. This represents the best case scenario if you follow all of the standard best practices.

How can I know how whether your time-to-inbox is comparable to other providers?

For now, the short answer is that you can’t. While it’s very common for email service providers to measure and record the Inbox Rate, none (other than Postmark, of course) are sharing how long it takes for emails to get to the inbox. Rest assured, we’re very confident sharing these numbers because we know where we stand against other email service providers. Since we focus exclusively on transactional email, we have a distinct reputation advantage that helps ensure our emails get to inboxes incredibly quickly, especially when compared to providers who also offer bulk marketing email capabilities.

Will all customers see delivery rates this good in practice?

Absolutely. Great delivery is included for all of our customers, free or high volume. We don’t think that great delivery should be an add-on or up-charge, and we stand behind our email delivery on both our shared and dedicated IP addresses.

System Availability

What different status icons and colors mean?
  • UP All systems operational
  • MAINTENANCE Maintenance
  • DELAY Delays
  • DEGRADED Degraded performance
  • DOWN Downtime
Where does this data come from?

The uptime percentage comes from Pingdom checks that happen every minute and represents the total downtime across all services. For example, if the API is down for 2 minutes and SMTP is down for 3 minutes, that would be considered 5 total minutes of downtime.

The timeline with the red, green, and yellow bars is driven by our content management system. Any day in the last 90 days that has downtime or degraded performance will be represented by a different colored bar in that graph with full details and an explanation of what caused the incident as well as the significant events and updates during the incident.

What qualifies as downtime?

If any Postmark service is unavailable for even a moment, it’s downtime. This includes planned maintenance if it requires taking services offline.

Postmark Services

Where does this data come from?

All data for our services and their response times are measured and reported by Pingdom checks at one minute intervals. Pingdom monitors each of the relevant endpoints for these services in one minute intervals from multiple locations. Each Pingdom check closely represents what our customers can expect. For instance, the API check is a full HTTPS check against an endpoint requesting and returning real data, opposed to a simple port check.