Dirk St?cker:
> For some subdomains when switching from catchall to individual settings I
> simply set a CNAME to another name with correct MX settings
>
> name.domain.tld --> mail.domain.tld (containing A,AAAA and MX)
>
> It worked for many servers, but some started to deliver mail to
> [email protected] instead of [email protected]. They shouldn't
> rewrite the mail address, should they?
That goes back to RFC 821. RFC 2821 explicitly allows aliases in
commands. Postfix still has a now-unused smtp_unalias module to
replace domain name aliases in MAIL FROM and RCPT TO.
RFC 821:
3.7. DOMAINS
Whenever domain names are used in SMTP only the official names are
used, the use of nicknames or aliases is not allowed.
4.1.2. COMMAND SYNTAX
Hosts are generally known by names which are translated to
addresses in each host. Note that the name elements of domains
are the official names -- no use of nicknames or aliases is
allowed.
RFC 2821:
3.6 Domains
Only resolvable, fully-qualified, domain names (FQDNs) are permitted
when domain names are used in SMTP. In other words, names that can
be resolved to MX RRs or A RRs (as discussed in section 5) are
permitted, as are CNAME RRs whose targets can be resolved, in turn,
to MX or A RRs. Local nicknames or unqualified names MUST NOT be
used. There are two exceptions to the rule requiring FQDNs:
- The domain name given in the EHLO command MUST BE either a primary
host name (a domain name that resolves to an A RR) or, if the host
has no name, an address literal as described in section 4.1.1.1.
Wietse
