On Fri, 23 Jun 2006, Ross Boylan wrote:
> Inspired by $spam_report, I'm looking for some details about how exim
> handles header folding, including folding from string expansions.
It doesn't.
> First, does exim ever add header folding on its own, e.g., if the lines
> would be long?
No.
> Second, I gather the standard way to do multiple lines is, for an ACL,
> add_header = X-Foo: some text\n\
> line 2, with at least one space at the start
Not quite, because Exim ignores white space at the start of continuation
lines in its config. You need
add_header = X-Foo: some text\n \
line 2
Note the space after the \n. You can also use this technique for adding
more than one header, or you can use:
add_header = X-Foo: xxx
add_header = X-Bar: xxx
for the latter.
> What if you have
> add_header = X-Bar: $var
> ?
> Should $var expand to the literal text that includes \n\ (where those
> are literal slashes, not escape characters), or can it have the
> characters directly?
If $var contains literal slashes, they will be inserted as literal
slashes unless you write ${expand:$var}. If you do that, or if $var
contains actual newlines, they will act as newlines.
> I assume that the separator should be \n (the escape character), not a
> CRLF, since exim operates using the former according to section 43.2
> "Line Endings". Right?
Correct.
> I've been concerned about the operation in an acl, as described in 39.19
> "Adding header lines in ACLs", but that indicates that adding headers
> works a bit differently in other parts of exim. If there are any
> differences in this area, I'd like to know.
The main difference is that you can have more than one add_header
modifier in an ACL, but only one add_header option for a router or
transport.
--
Philip Hazel University of Cambridge Computing Service
Get the Exim 4 book: http://www.uit.co.uk/exim-book
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