On Tue, Apr 16, 2019 at 04:38:54PM +0100, Jeremy Harris via Exim-users wrote:
> The 998 limit is for de-folded lines. Go over that and you'd need
> multiple header lines; to do which you'd have to be duplicating
> header_names: as well as adding linebreaks. And yes, that would
> very likely break DKIM signatures.
That'd be a rather unexpected Exim behaviour. SMTP limits "physical"
lines to 1000 bytes (including the CRLF), but there is no such limit
on folded headers, and many headers are "single instance" and must
not be present more than once.
Postfix allows a *folded* header of up to 100k bytes by default,
and the limit is configurable. This is a per-logical-heade limit.
The overall header size is not limited, but IIRC more than 64KB of
headers total may not work once milters are configured, due to
limitations of the milter protocol.
--
Viktor.
