The problem lies in the CLIENT, not SERVER.
The server works fine, and the client works fine, receiving mail normally.
The problem is when the user, in the IMAP client, selects to "backup"
or "export" the mails to harddrive.
This will cause *.eml or *.msg files to be written to a user-specified
folder, for example a USB thumb drive on computer, local storage in
the Android phone, or whatever, depending on how that IMAP client
works.
The problem is that these IMAP clients, then directly write the
subject as a file name, and of course some characters are not allowed
as file name, and some subjects are too long, causing the operating
system to reject the filename.
This in turn is unhandled in the IMAP client, causing it to suddenly
crash during copying.
Thats why I have to fix it on server end, so the user's IMAP client is
never fed a email that would fail backup later, if the user wants to
backup his own email himself.
Theres no problem at server end, no problem in exim, no problem in
dovecot. The problem is the IMAP client at user end, failing to handle
specific email subjects.
Because its a hell to track down if the user has like 500 emails in
the inbox and client crash somewhere like after 231th email being
copied, and then user have to find the culprit email in their inbox
and then delete it, for the user to succeed copying without crashing
the client.
Den ons 28 nov. 2018 kl 10:44 skrev Andrew C Aitchison <andrew@???>:
>
> On Wed, 28 Nov 2018, Sebastian Nielsen via Exim-users wrote:
>
> > How can I reliably cut subjects that are too long, without breaking
> > for example quoted-printable encodings and such?
> >
> > Ergo, if the subject line exceeds X characters (where X characters are
> > a limit I as system administrator decides) it should just truncate the
> > decoded subject line, reencode it, and then send the mail along.
> >
> > The reason I want to do it, is because some IMAP clients do crash when
> > it tries to export/backup email with too long subject lines as it
> > tries to write the subject as a filename, and the operating system
> > returns a error code the IMAP client don't understand = crash.
> >
> > Also I want in the same way, filter away all and any emojii (for
> > example the truck in Ebay's "Order is now being delivered" emails)
> > from subject lines because emojii also causes these IMAP clients im
> > talking about to crash (because obviously emojii can't be used as
> > filenames), and emoji in email subjects are so useless so im
> > speakless...
> >
> > Any ideas?
>
> Which format is exim using to save messages: unix mailbox, MBX, maildir,
> mailstore ?
>
> I'm surprised thst you are using the subject as the filename; you
> certainly don't have to do that; the appendfile driver for the
> local_delivery transport allows you to set the filename exim uses; you
> have presumably explicitly set this to include the subject line, so
> can change it to something else ?
>
> Which IMAP *server* is causing these problems ?
>
> --
> Andrew C. Aitchison Cambridge, UK
> andrew@???
>
