Hi Wietse, > On Oct 11, 2017, at 7:11 PM, Wietse Venema <wie...@porcupine.org> wrote: > > J Doe: >> Hi, >> >> I have a syntax question regarding configuring mandatory TLS encryption for >> the smtp process as listed on: www.postfix.org/TLS_README.html#client_tls >> >> In the second example on the page, square brackets are used when specifying >> the policy for specific destinations in the tls_policy file: >> >> /etc/postfix/tls_policy >> [example.net]:587 encrypt protocols=TLSv1 ciphers=high > > You need the [] and the :587 in the lookup key, if that is what you > specify as the destination in relayhost, transport_maps, etc. > > Wietse
Thank you for your reply. Ok, I understand that I would need that if the hostname was specified in relayhost, etc. but I am still confused as to what the square brackets mean. A previous reply to this thread from /dev/rob0 (thanks rob0), states: “The [] enclose a hostname which is to be looked up as a type A or AAAA record. Without the [] first a lookup of type MX is done, and where found, prioritized lookups of further hostnames (A or AAAA) would be done. This is not specific to TLS, it is common to transport(5) and many similar Postfix features. The reason being, MX records exist to control mail routing.” Does this mean that the square brackets determine the strategy for determining the address of the mail server ? Thanks, - J
