This question is not postfix-related .... so its somehow off-topic.
But it's related to mail systems, so i cant imagine any other place to
get some help on this subject.
I have a domain (domain.com.br) with lots of subdomains in the
nnn.domain.com.br (about 40 different subdomains) have only 2 (two)
nnn IN MX 10 server.nnn.domain.com.br.
nnn IN TXT "v=spf1 include:domain.com.br -all"
there's absolutely no A entries for the subdomains.
i'm having an isolated problem with a customer that cannot send
mails to one of my subdomains (everything else is working fine, several
thousand of messages flowing daily, this really seems to be an isolated
problem). Altough, their sysadmin (from the domain which cannot send us
mail) is telling what i'm doing (having an MX entry but no A entries) is
RFC-illegal, altough he cannot point me which RFC i'm not complaining with.
i really dont know if this setup (MX record but no A record) is
RFC-OK. The only think i know is that it's been working for years and i
receive thousand of emails daily on my several subdomains with no
problem at all.
question is .... do a domain (or in my case, a subdomain) *MUST*
have an A record ? Is the config i'm doing (DNS speaking) correct or
incorrect (RFC-speaking) ??
Thanks for any hints on that ....