Newsletter looses advanced settings when updated

When a newsletter is edited after sending it looses its advanced settings (mail format, receive request and priority). When you edit the newsletter node before batch (cron) sending is completed you may experience that (a number of the) html email are send as plain text. The attached patch solves this. Patch will be available in the next 6.x-1.x-dev release.

To verify whether you have this problem or not, check the simplenews_newsletter table's 'format' field. This field normally contains 'plain' or 'html'. If this field is empty you have edited the node after sending and a part of the newsletters is send in plain text.