This issue occurs when using CiviCRM and the new Mosaico designed newsletters.

If you have a mailing list of 1,000 or more subscribers and your content is engaging, chances are pretty high that you have unfortunately experienced this problem: You hit send! Your awesome newsletter goes out and next thing you know, your website starts to slow down and eventually stops responding. What’s happening? We are often faced with this question in Agileware Support queues.

This is how we all feel when your website slows to a crawl

The culprit for this type of issue has been elusive and we thought, fixed a number of times. Well now, I am proud to announce that we have finally fixed the issue and sending newsletters out to a large audience of subscribers will no longer trigger a site outage.

The problem was primarily due to some poor design decisions when embedding images in a Mosaico designed newsletter. Images are automatically resized, but this resizing is done on-demand and the resized image is not re-used. Consequently, the image is resized for each email delivered. This simply does not scale and can quickly bring the fastest of servers to a grinding halt.

Agileware has incorporated this performance enhancement into our CiviCRM build which is being pushed out with the CiviCRM 5.16.3 update.

If you have been updated to CiviCRM 5.16.3, then your site will benefit from this fix immediately.

About the author Justin rotate

Director at Agileware. Justin has been developing and supporting software since the 90s. A strong advocate of free software and good customer service.

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