Remove "format=flowed"

[mxmehl]

Astroid sends email with the header Content-Type: text/plain; charset=utf-8; format=flowed. The last part seems to create some embarrassing line breaks, especially when writing longer lines than 76 encoded characters (or umlauts which stretch the editor's wrap width after encoding).

Anyway, format=flowed seems to be a rather broken standard, and most mail clients don't use it (any more). Is there any reason astroid uses it? And would it cause issues when removing it?

[mrvdb]

Please keep it as an option

[kirschner]

I also had quite embarrassing problems with that, as the e-mail looked absolutely unprofessional because of that bug. Thanks @mxmehl for researching and reporting!

[mxmehl]

Perhaps as additional info: The bug only seems to occur on mail clients which support format=flowed. In my and @kirschner's case this was on Claws Mails IMHO.

[kirschner]

First time I got that feedback was from an Evolution user, though.

[mrvdb]

@mxmehl Are there more details on the bug other than "embarassing line breaks" ? I've been a long time claws user and migrated to astroid from it.

[mxmehl]

I don't have a screenshot to share but I'll try to explain.

In vim I have a fixed line width of 72. In quoted-printable, the maximum width is 76 characters. For example, if you use special characters like umlauts which are escaped by quoted-printable you exceed the 76 character limit. A raw text therefore could look like this (3 lines):

Bj=C3=B6rn, k=C3=B6nntest Du mir bitte die besagte Mail komplett forwarden?=
 Dann
gucke ich mal, ob man da was herausfinden kann.

In my original text, Dann was on the first line, and after it came a normal line break. The = at the end of the first line indicates a soft line break which shouldn't be visible after decoding quoted printable. So in the end, it should be 2 lines.

On a client which respects format=flowed, this looks like:

Björn, könntest Du mir bitte die besagte Mail komplett forwarden?
 Dann
gucke ich mal, ob man da was herausfinden kann.

So format=flowed seems to interpret the soft line break as a hard line break.

And since the = is also used as escape character, the wrong interpretation also causes umlauts to break. This happens if an escaped umlaut (e.g. =C3=BC for ü) is cut in between by a soft line break:

W=C3=BCrde mich freuen, wenn wir dieses Jahr xxxxxxxxx als yyyyyyy begr=C3=
=BC=C3=9Fen
d=C3=BCrfen.=20

I'm not quite sure how the = character is handled with format=flowed and quoted-printable but at least in Claws it breaks lots of things.

[jlombera]

This is not a bug. Please take a look at https://www.ietf.org/rfc/rfc2646.txt to understand how to f=f works and how compliant clients are supposed to format these emails. In any case, please leave this as an option, since is a very useful feature for plain text emails (hard line breaks are a nuisance in deep quoted messages in a thread).

[gauteh]

FYI, in VIM you can use: {gq} to re-wrap a quoted paragraph. It can be added as an option, PR's welcome - shouldn't be too hard.

[gauteh]

According to the standard (ref #446 (comment)) the editor should wrap lines according to some rules. In VIM this can be probably be achieved with textwidth and friends. If anyone has any good defaults for this (not already included with the standard ft=mail?) please share!

[gauteh]

Fixed in #463. Now configurable.

[gauteh]

https://github.com/astroidmail/astroid/wiki/Configuration-Reference#mailformat_flowed