Open Tracking

Open tracking is enabled per SMTP User, authenticated IP address (IP Authentication), or API key.

To enable open tracking for an SMTP User, visit the "
Sending > SMTP Users > Select your username > Tracking & Status > Open Tracking" section of your account’s dashboard:



Once enabled, you'll then have the ability to see if an email was opened, as well as an estimate of how long it was opened, from the "Reports > Activity" section. This information can be viewed from the "Timeline" tab upon selecting the recipient address via the right-hand column. If an email is opened multiple times by the recipient then multiple ‘Opened’ events will be added to the timeline.



This data is also available through API requests and Webhooks.

How does Open Tracking work?
When you send an HTML email with Open Tracking enabled, SMTP2GO will embed a transparent 1x1 pixel image into the email. The image URL contains a unique token and when the image is loaded from our tracking servers (e.g. the image is loaded when the email is opened in the email mailing client) it causes an "open" event to register based on the information encoded into the token.


  • Open tracking is not available on plain text emails as we can only add the tracking image to HTML emails.
  • If a recipient views the email in a mailing client that blocks images from loading, open events won't be recorded.
  • Gmail - If the recipient views the email via the Gmail website or mobile app it will display images served through a proxy server. If the image is pre-cached (opened by Google's image proxy) or loaded in the mailing client way there isn't a way to distinguish between the two which can mean there's no way to 100% guarantee the recipient opened the email.
  • Apple Mail - Starting in iOS 15, Apple allows iOS users using Apple Mail to turn on a setting called Mail Privacy Protection that can cause false-positive opens to be reported and is designed to stop senders using invisible pixels to collect information e.g. open tracking.


If you have questions in regard to Open Tracking or any other part of the SMTP2GO service, please reach out to our award-winning support team for assistance.

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