I absolutely agree 
E.g. The man in the middle have first got access to the Mailaccount of Alice or Bob or have to break the transport encryption.
My theoretical scenario can only used as a direct attack to a special communication and is very hard to realize.
There is no way for attack masses of communications automated.
That’s why I said “theoretical”.
I’m sure for the normal hacker it’s nearly impossible and much to expensive.
Let’s stay on topic please. Leaking info in the Subject is a good point, but DC doesn’t do that. We are discussing Subject for unencrypted emails.
I don’t think so. There would be 3 possibilities that come into my mind:
My favourite one: Let the user enable or disable a row of checkboxes: (they won’t be able to change the order then, but I actually think that this reduces confusion)
[Prefix] – and let the user specify the prefix, such as “Chat:”
[Group name]
[First few words of the message]
[Existing subject] (works only if this is a reply)
From WinAuthFan: Let the user choose a template string like Chat: <firstwords> in which all occurences of firstwords are replaced → will need documentation but should actually be quite easy to implement.
Just give some possiblities like Re: [subject] the user can choose from (easy to implement and no need to explain but not that customizable)
I definitely think that the effort is worth it.
I think that dc subjects needs a rework, I don’t like the piece of body in the subject, (even some user complained about it, because “the message body is protected by the law(it is illegal to check it), but the subject isn’t”
Anyway I don’t think letting the user select the subject format would be good nor for users nor for developers 
if users needs to write an email instead of a chat message what they need is a email view in Delta Chat: [Discussion] Make DC a replacement for MUAs? - #12 by testbird
You could just default the Subject to “Delta Chat” or “Chat”. This would be ignored by the app but email only users would only have this as their subject line. It is simple and doesn’t compromise security issues. This would also group message for email users on subject to the same recipient.
That’s true.
Nevertheless, including the chat text in the subject is a nice way to provide some degree of improved chatting experience when writing to MUA-only contacts. Allows them to follow the conversation right in their message listing or browsing overview.
-[] Hi, meet for lunch, today? |
Re: Yes, but I'll be 15min late.
I still would prefer for Groupchats a subject like:
“Groupchat: Group name”.
Because users of regular mail clients will be allways remembered it’s a group chat and they have to use “replay to all”.
And also if they in more then one group, they will know what’s the topic of THIS group.
A classic (MUA) way to indicate mailing lists (group chats) is to prefix the short name using square brackets. That’s why I think the “-[]” prefix I propose would also fit in nicely with that, if it contains the group name in case it’s group chat:
-[deltachat-testers] I like the backwards compatible, refining enhancements.
That may warrant a “only use empty or generic subjects” option.
I think that would improve email compatibility to standard MUAs as it would help to maintain threads of conversations grouped properly.
I like the idea! 
Thank you @luisfsr.
And a nice side effect woul be - MUA users would realize it’s not a normal mail. It’s a messenger message
And probably he/she will become curious what’s Delta Chat.
So maybe it’s a good publicity.
-[Subject of emails] Unencrypted messages already mention|
-[Subject of emails] https://delta.chat in the body (footer).|
-[Subject of emails] Using the subject as in these examples, by default,|
-[Subject of emails] can be a nice way to provide a chat view|
-[Subject of emails] even to classic MUA users.|
And supporting a separator like...
E-mail body:
And supporting a separator like… - (minus) would already allow the user to manually specify the subject and write a classic email in the messenger (in the same way received subjects are shown). See this thread for further details: Subject and Group names · Issue #128 · deltachat/deltachat-core · GitHub
(PS: The references header (already used) or possibly in-reply-to is there to allow for the proper grouping of the messages in classic MUAs. So there is no need to rely on (fixed) subject texts.)
I simply don’t like if the subject is made of a part of the body. It’s not really a problem but also not nice.
+1
DC uniqueness - it is simplify email messaging AND automatic encryption.
Attempt to seat on two different chairs, located in opposite corners of room, that what this tread all about IMO.
KISS principle - do one thing, but do it best.
If one need full feature email messaging, then he/she should use full feature email client such as thunderbird for example that allows feature one needed.
Personally I really don’t like that DC attempting to act as a normal email client for un-encrypted messaging. It defeat the whole idea of simplified messaging, idea to be a secure chat application. It may create situation when encryption will be broken logically by simply messing encrypted and un-encrypted messages.
Chat != email
Use the right tool for a job - is an old wisdom verified by time.
There are plenty of email clients that satisfy requirements to supply custom subject as well supporting encryption. Why one more ?
Just download a normal email client and use it.
Blue Mail, Email by Edison, Microsoft Outlook, Gmail, Aqua Mail, Email TypeApp, K-9 Mail, myMail, Newton Mail, ProtonMail… and so on, just choose your favorite tool instead of breaking unique features of DC and move it to the list of highly competitive apps listed above.
Adding geek’s “-” or “|” separators easily can be abused by people who have no clue about such proposed feature (I think it is majority of users who don’t like to read documentation) and DC will easily became non encrypted chat app.
While DC is technically a MUA, the gist of this app, that it is a chat app.
There no such thing as a subject in chat applications.
One more time: Use the right tool for a job - is an old wisdom verified by time.
Please stay at the topic. Your post could belong here: [Discussion] Make DC a replacement for MUAs?
And there are people who would like to use DC as MUA (-> email interop) (like, me); we already had all pro and con arguments in the linked thread I think.
@AlexJ the problem is that Delta Chat can’t work nicely in a multi-client setup (Delta Chat + classic MUA): notifications from your classic MUA and from DC for the same message, self-bcc copy notification from your classic MUA, double downloading of messages, etc.
for this reason people would like to have the right tool for the job and use only Delta Chat, anyway as @Hocuri said this probably better go to [Discussion] Make DC a replacement for MUAs?
I think all your concerns can and need to be well incorporated in the right solution.
I simply don’t like if the subject is made of a part of the body.
-” proposal)DC uniqueness - it is simplify email messaging AND automatic encryption.
Exactly, and that means to be able to communicate seamlessly with all types of email clients, classic and chat clients.
KISS principle - do one thing, but do it best.
That’s why deltachat-core only provides the messaging programing interface (API) to the email system, and needs to incorporate all the functionality to make it operate smoothly within the entire email world.
Personally I really don’t like that DC attempting to act as a normal email client for un-encrypted messaging. It defeat the whole idea of simplified messaging, idea to be a secure chat application. It may create situation when encryption will be broken logically by simply messing encrypted and un-encrypted messages.
Your use-case (Use-cases, chat rules and configuration options) then sounds like you may want to use the “require encryption”, or maybe better a “prefer encryption, without fallback to unencrypted” preference, or “secure chats”.
Adding geek’s “-” or “|” separators easily can be abused by people who have no clue about such proposed feature (I think it is majority of users who don’t like to read documentation) and DC will easily became non encrypted chat app.
I currently don’t understand why or when using “-” (and even “|”) should trigger a fallback to sending unencrypted messages, that would be wrong IMHO. For those using chat apps (no subject field), there won’t be any visible difference, anyway.
Concerning the “geekness”, that’s only the quick option for the email aware users, directly accessible by typing the messege. GUI is possible later: Subject and Group names · Issue #128 · deltachat/deltachat-core · GitHub
While DC is technically a MUA, the gist of this app, that it is a chat app.
There no such thing as a subject in chat applications.
A very unique DC feature is the large existing (classic) email user base. Currently, most of these contacts use email clients with subject fields, and deltachat therefore has to find a way to communicate decently with all of them as well.
BTW: The suggested chat-mode subject line format (chatting with peers using classic email clients) like
-[] Text... |
and
-[group name] Text... |
should be better than the curren Chat: Text..., because it is shorter, the symbols should work in any language, and the automatically but conditionally added, closing | allows deltachat to indicate that there is no need to download the whole email body, as there is no further text missing.
And together with always sending attachments in separate emails (to be downloaded only when desired), it also allows to mark those chat messages as containing no text, but only an attachment (-[] |). Making unnecessary, potentially expensive downloads optional.
The classic-mode subject line handling (for non-chat messages) would just resemble the behaviour of classic email clients.
A very obvious subject indication and naturally-feeling, manual editing mode:
I found Delta Chat a few days ago (google play v0.200) and love the idea. But I absolutely hate the subject munging. It completely breaks decades of e-mail precedent.
A major talking point is that we can use DC to chat with regular e-mail users. But…
From my user standpoint, e-mails are grouped by subject (topic), not by members in the cc:. people get added, removed, it’s still the same subject. The subject finished, the same members may create a new topic. The old topic is archived.
Usage case: my friends and I are planning an outing. We don’t have identical chat. SMS sucks. Signal vs. whatsapp vs. facebook vs. etc. We all plan via long e-mail reply threads. This theoretically seems the ideal case for DeltaChat. But it’s not working. It’s broken on the email MUA since subjects are changed. It’s broken on DeltaChat since people get added and removed creating multiple groups/chats/conversations. It’s not working with people who use e-mail.