I have had “WP Mail Logging” running for over a while now and once again a mail has been delivered with no image links. Unfortunately, the log only says that two mails are sent. Once with images and once without. All other mails are delivered only once. The faulty ones twice. That is quite strange. And especially the first one (with the picture links) is not sent. But I can’t find anything wrong in the log. They look completely identical from both mails, just have the difference that the thumbnail images of the picture are with and without link (a href).
I still have the debug mode on now and wait until it happens again. I will report back then.
But I do not have an idea. Mainly because I can’t reproduce it.
Do you have another idea?