I am trying to use the "Default user E-mail suffix" setting to avoid duplication in the "Default Recipients" list, but it doesn't seem to be working. For example:

With this configuration, I expect Email-Ext to append the default suffix to each entry in the default recipients list. This does seem to happen, as the log reports

Checking if email needs to be generated
Email was triggered for: Always
Sending email for trigger: Always
messageContentType = text/html; charset=UTF-8
Request made to attach build log
Request made to compress build log
Adding recipients from project recipient list
Adding recipients from trigger recipient list
Setting In-Reply-To since last build was not successful
Successfully created MimeMessage
Sending email to: john.doe@foo.com jane.doe@foo.com

But the email does not appear to be sent. At least, I'm not receiving anything.

However, with the suffixes manually appended to each entry in the default recipients list:

The emails are sent without issue. What's going on here?