Missing line breaks in Newsletter e-mails.

[Friedrich2]

Affected version(s)
3.5.19, occurs probably in newer and older versions too.

Description
Newsletters sent with Contao Newsletter do not have proper newlines. To give an exemplary excerpt of a manually obfuscated newsletter's source code:

xxx n=C3=A4 xxxx =
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx=
xxxxxxxxxxxxxxxxxxxxxxxx.

xxxxxxxxxxxxxxxxxxxxx

As you can see, line breaks / newlines / paragraph endings (I do not know which types Contao does know and support) are marked with line newlines in the source code, sometimes with an added equality sign.
The problem is simple: Line breaks are not displayed in HTML per default (except in cases where a specific CSS attribute is set or under somewhat special other circumstances).
From my point of view, the newsletter should add <br /> tags or some other HTML stuff to display line breaks additionally to newlines in the source code itself.
Another, more elegant idea: Is it possible to deliver a message in two different formats Only-Text and Fully-Fledged-HTML within one message and without that the normal recipient knows about it?

Is anyone able to reproduce the problem?

And: What do these equality signs mean? They seem to be ignored.

How to reproduce
Send an e-mail including line breaks via the newsletter system. The line breaks should not be displayed in the recipient's e-mail program. (It is necessary, that at least the level »Simple HTML« is set in Thunderbird main window -> View -> Message Content .)

[asaage]

You should be able to send newsletter as text/plain or multipart/alternative content even in 3.5.19 (which you should probably update).
The latter one basically delivers the message in text and html format (HTML content & Text content should both not be empty and the checkbox Send as plain text unchecked)
I never experienced any problems with linebreaks.
For the text-part simply hit Enter.
For the html-part Enter generates a new paragraph Shift+Enter generates a linebreak (depending on css and mail-client you might see no difference between them).
Equal-signs are probably from quoted-printable encoding and only be shown in the source code of the message itself.

[fiedsch]

And: What do these equality signs mean? They seem to be ignored.

I'd say it is there because the text is "quoted printable" (see the example in https://de.wikipedia.org/wiki/Quoted-Printable-Kodierung)