On one of my websites, any Acymailing newsletter is being sent in text/plain format.
The preview is ok, but the test mail that I receive is in text/plain format and begins with the following lines:
This is a multi-part message in MIME format.
--b1_oR3xdKDCHLaYpsC1urxOIQXrApm8akKg2hpRg3gcE
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
On the second website, the newsletters are beingt sent in HTML format.
In «Configuration > E-Mail-Settings» there are exactly the same settings.
Thank you and kind regards
Chris