**Optimizely experienced a 75+ hour incident in which email campaign messages were partially dropped for North America region accounts.** The root cause was a SendGrid configuration change that introduced an incompatibility in email header processing, disrupting delivery for affected campaigns. Optimizely deployed a workaround to restore delivery and is working with SendGrid on a permanent fix; notably, delivery records for the affected period are unavailable, meaning campaign re-runs risk sending duplicate emails to some recipients.
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This incident has been resolved.
We are continuing to monitor for any further issues.
We have deployed a fix to unblock affected customers and are actively monitoring the system to confirm stability. We are also working with our email vendor (SendGrid) to put a more complete solution in place on their side.
Please note: during the period when emails were partially dropped, we do not have a record of which individual recipients successfully received messages. As a result, if you choose to re-run an affected campaign (e.g., by sending it to a new campaign), some recipients may receive duplicate emails.
We will provide a further update as monitoring continues.
We have likely identified the root cause as a recent SendGrid change that introduced an incompatibility in header processing. We are sharing our findings with SendGrid and implementing a workaround to restore compatibility.
We are still looking into this issue and will provide updates as they become available.
We are continuing to investigate this issue. We also have a support thread open with Sendgrid.
We are investigating an issue causing some email campaign messages to be dropped in the North America region. Some emails are still being delivered. Accounts using email campaigns in the region may be affected.
We will update as we learn more.
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