HUGE RETRACTION: I've really messed this up...
At the time of the HELO/EHLO command, SMTPD_FLAG_SMTPUTF8 should always
be false, that feature may be negotiated after HELO/EHLO.
As such, the UTF8 handling code of reject_non_fqdn_hostname is ALWAYS
DISABLED during HELO/EHLO and so
"reject_non_fqdn_hostname" and "reject_invalid_hostname" behave
identically as far as character set permitted.
Differences between the two are that:
"reject_non_fqdn_hostname" requires at least one "." and requires a
literal address be in square brackets.
"reject_invalid_hostname" permits unbracketed addresses (somehow missed
in earlier discussions).
To try and restore some clarity, I've made a little table that goes
through several forms of name that may be thrown at Postfix.
"G" is "Good", the rule will NOT Reject the name in HELO/EHLO
"B" is "Bad", the rule WILL Reject the name in HELO/EHLO
+---- "reject_invalid_hostname"
| +-- "reject_non_fqdn_hostname"
| |
v v
B B {UTF8}-hostname.domain ( n.b. SMTPD_FLAG_SMTPUTF8 should always be
false at time of HELO/EHLO )
G G xn--hostname-{punycode}.domain ( n.b. SMTPD_FLAG_SMTPUTF8 should
always be false at time of HELO/EHLO )
G G xn--hostname-rubbish.domain ( n.b. Postfix does not decode
punycode in HELO/EHLO )
G G hostname.domain
G B hostname
G B 12.34.56.78 {non standard}
G B 0123:4567:89AB:CDEF:0123:4567:89AB:CDEF {non standard}
G B 0123:4567:89AB:CDEF:: {non standard}
G B 0123:4567:89AB:CDEF::12.34.56.78 {non standard}
B B #12 {non standard}{ numeric form allowed in RFC821 }
| | **Both rules deal with square brackets identically**
G G [12.34.56.78]
G G [IPv6:0123:4567:89AB:CDEF:0123:4567:89AB:CDEF]
G G [IPV6:0123:4567:89AB:CDEF::] {n.b. RFC2821 only specifies
"IPv6", this in non-standard}
G G [Ipv6:0123:4567:89AB:CDEF::12.34.56.78]
B B [0123:4567:89AB:CDEF:0123:4567:89AB:CDEF] {"IPv6:" tag is mandatory}
B B [Ipv6:0123:4567:89AB:CDEF:0123:4567:89AB:CDEF/128] {CIDR extension
not allowed}
B B [12.34.56.78/32]
B B [ ipv6:0123:4567:89AB:CDEF:0123:4567:89AB:CDEF ] {whitespace is
not allowed}
B B [ IPV6:0123:4567:89AB:CDEF:: ]
B B [ IpV6:0123:4567:89AB:CDEF::12.34.56.78 ]
B B [ 12.34.56.78 ]
B B hostname.domain [12.34.56.78] { this form not allowed in HELO/EHLO }
Sorry for all the confusion.. Hope this clears things up a little.
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