${sg{abcdefabcdef}{abc}{xyz}}
.endd
yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
-if any $ or \ characters are required in the regular expression or in the
+if any $, } or \ characters are required in the regular expression or in the
substitution string, they have to be escaped. For example:
.code
${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
.option dkim_private_key smtp string&!! unset
.option dkim_canon smtp string&!! unset
.option dkim_strict smtp string&!! unset
-.option dkim_sign_headers smtp string&!! unset
+.option dkim_sign_headers smtp string&!! per RFC
.option dkim_hash smtp string&!! sha256
.option dkim_identity smtp string&!! unset
DKIM signing options. For details see section &<<SECDKIMSIGN>>&.
CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
BDAT will not be used in conjunction with a transport filter.
-.option hosts_try_fastopen smtp "host list!!" unset
+.option hosts_try_fastopen smtp "host list&!!" unset
.cindex "fast open, TCP" "enabling, in client"
.cindex "TCP Fast Open" "enabling, in client"
.cindex "RFC 7413" "TCP Fast Open"
On (at least some) current Linux distributions the facility must be enabled
in the kernel by the sysadmin before the support is usable.
+There is no option for control of the server side; if the system supports
+it it is always enebled. Note that legthy operations in the connect ACL,
+such as DNSBL lookups, will still delay the emission of the SMTP banner.
.option hosts_try_prdr smtp "host list&!!" *
.cindex "PRDR" "enabling, optional in client"
unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
variables here.
-.option dkim_sign_headers smtp string&!! unset
-If set, this option must expand to (or be specified as) a colon-separated
+.option dkim_sign_headers smtp string&!! see below
+If set, this option must expand to a colon-separated
list of header names. Headers with these names will be included in the message
signature.
When unspecified, the header names recommended in RFC4871 will be used.
+The default list is available for the expansion in the macro
+"_DKIM_SIGN_HEADERS".
.section "Verifying DKIM signatures in incoming mail" "SECID514"