I use newsletter (for free) since 2014 and never had problems. At 4th of January in 2016 I sent the last newsletter which was OK.
Now I wanted to send a new newsletter. I sent this to the test user. The received email was very bad! The formating was wrong, there are gaps in the words, German letters (ÄÖÜ) were absent.
However, in the on-line view is all OK, exact like in the original. Presumably this deals with any update at all?
Please, around help!
(Sorry for my English)
Uhm it seems more a problem of the mail server changing something in the newlsetter, specially since you report the characters are not shown in the right way (in Italy we have the same “special” characters so I’m aware of this kind of problems).
Try to send me a test newsletter at email@example.com so I can see the wrong chars and try to understand why. Try even to change the encoding available in main newsletter settings.