On Thu, 18 Nov 2021 21:03:43 -0000 (UTC)
Jasen Betts via Exim-users <exim-users@???> wrote:
> On 2021-11-18, Andrea Biscuola via Exim-users <exim-users@???> wrote:
> > Hi all
> >
> > We are an italian hosting provider (https://host.it) and we use exim to relay e-mails from
> > our hosting servers.
> > Exim is installed and configured through the directadmin control panel
> > (https://www.directadmin.com), so the main configuration is managed using the
> > directadmin custombuild subsystem.
> >
> > One week ago, we upgraded to exim 4.95 and suddenly, some customers (using microsoft
> > outlook, nonetheless), started to experience the following error for *some* of their
> > e-mails:
>
> Outlook is not email software. Outlook is X.400 software with partial email
> capability tacked on.
We all agree on that.
>
> > message has lines too long for transport
> > Reporting-MTA: dns; web017.shared.host.it
> >
> > I received some examples of such e-mails from our customers service, and it appear that
> > the problem is with some badly formatted headers.
>
> > Unfortunately, we can't throw those customers out of the window :-) so we are searching
> > how to expand the line limits for the transports.
>
> Turn off 8BITMIME. that may be sufficient to prevent this outlook bug.
> perhaps configure two different submission ports one with 8BITMIME
> disabled for the benefit of those afflicted with outlook and one with
> all the features enabled.
On another thread it was mentioned that it could be possible to fold the "References"
header, splitting it on multiple lines.
I think it could be a better solution than increasing the limit, would that work?
>
> > However, I'm struggling to understand, from the documentation, what the correct solution
> > is. From what I was able to understand, we should modify the remote_smtp and
> > remote_smtp_forward_transport sections to solve the problem, with the message_linelength_limit
> > parameter set to something like "4096".
>
> The important documentation is here:
> https://datatracker.ietf.org/doc/html/rfc5322#section-2.1.1
>
I already checked the relevant RFC, thanks.
> > Consider also, that the main exim configuration, is handled directly by directadmin and
> > it's generated from it's internal "templates". In general, we can safely change a configuration
> > file called /etc/exim.variables.conf.custom to put a series of overrides to the default
> > configuration.
> >
> > Do we need to modify the directadmin templates or can we use one of the "custom" files
> > in /etc to achieve the same result?
>
> Increasing that limit will break SMTP and will probably just result in the refusals
> taking longer to reach the sender.
>
Andrea
