On Wed, Oct 11, 2017 at 05:36:07PM -0400, J Doe wrote: > 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 > > Are the square brackets only required when the port to use is > specified (ie: in previous example when destination was example.net > with no port specified, I notice that the square brackets are left > out) or is this syntax specifying something else ?
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. -- http://rob0.nodns4.us/ Offlist GMX mail is seen only if "/dev/rob0" is in the Subject:
