After spending 20 more minutes to think about I'd go somewhat
more into detail:
If wanting to fetch the record for somedomain.com
do a DNS query for A, SRV and TXT record (or ANY) on
_lmap.somedomain.com (violates the SRV RFC a little bit, but
for sake of efficiency)
If a SRV record is found then
try the servers as described in the SRV records
elsif A records are found then
try on of them or one after another, Port 80
else
error, no record available.
end
If TXT record available then
run it through maxcro expansion for sender name, IP address,
MessageID,... and take this as the URL to query.
(if macro after first '?' then protect special characters as
usual in URL query parameters)
else
use default URL /_lmap/somedomain.com
end
-> Fetch record and evaluate
Hadmut