In order to investigate this, please attach a screenshot showing the settings from the “Subscription and posting” tab of your mailing list in Webadmin interface.
Additionally please follow the steps below:
maximize the log level under Queue -> Processing and save the configuration
maximize the log level under Services -> SMTP Receiving and save the configuration
Based on the screenshot there is no obvious problem with the list’s subscription settings, that would cause this behavior. To further investigate this situation I need the log file corresponding to one such failed subscription attempt as requested in my previous post.
If the forum does not allow you to attach the txt file or the archive, please consider copying and pasting just the content around the time frame when you replicated the problem.