breaking long header lines into 2 (or more) lines

[Ian Zimmerman]

On 2018-04-24 10:06, Matthias Apitz wrote:

> Long header lines can be split into 2 or more lines and the 2nd line
> must start with a blank (is TAB allowed too). Is there any rule (RFC)
> at which char the split is allowed or not allowed? For example, can
> mail addr lines be broken at any point like this one:
> 
> To: mutt-users at mut
>  t.org
> 
> I did tests before asking and such a case like the one with
> mutt-users at mutt.org above is arriving fine and the line is put
> together somewhere in the MTA chain.

That is odd, it shouldn't work.  According to the RFC cited elsewhere in
thread.

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