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.
> 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.
> 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
> 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.
--
Jasen.
