This time PLEASE refrain from sidetracking the discussion. I want
to know what will break when the default changes, if that is not
too much to ask for.
Summary:
Until now, Postfix has a default setting "append_dot_mydomain = yes".
This performs autocompletion from user@host to user@host.$mydomain.
But this default setting is becoming problematic.
I need to find out what will break when the default is changed to "no".
How many people expect that this change would be a problem? It *may*
affect mail that is submitted with the sendmail command line, or
aliases that expand to user@host instead of user@host.domain. Email
addresses in SMTP *should* already be fully qualified. But I also
know that the real world often does not behave as it *should*.
Hence this query to the postfix-users list.
Details:
Why is the default "append_dot_mydomain = yes", anyway?
- It can be "convenient" to send mail to "user@host" and to have
Postfix auto-complete the address to "user@host.$mydomain", or
to specify aliases to "user@host" instead of "user@host.domain".
Laziness is the primary reason append_dot_mydomain exists.
Why change the append_dot_mydomain default to "no"?
- The problem is that the current defauly produces incorrect results
*with Postfix default settings*, meaning it is my fault, I can't
blame the user, therefore something in Postfix needs to be changed
to fix this (and not just adding warnings to documentation).
Specifically, when the hostname is a registered domain such as
example.com or example.ac.uk, Postfix default settings will
auto-complete "user@localhost" to "u...@localhost.com" or
"u...@localhost.ac.uk". Both forms are clearly bogus.
- Some distributions already ship with "append_dot_mydomain = no".
This is an opportunity to eliminate the inconsistency.
Now, Postfix could know that it should not use a single label (".com"
etc.) as the default mydomain value, but there are two-label domains
like ".ac.uk" and even three-label ones that are equally inappropriate
(though I think that their number is much smaller than the number
of single-level names such as ".com", ".nl", etc.). So avoiding
single-label suffixes (".com" etc.) is not perfect, but it may still
be useful as a safety net.
The real fix is not to auto-complete email addresses. That requires
changing the default to "append_dot_mydomain = no". If people decide
to change this to "yes", then I can blame them for not reading the
warnings in the documentation :-)
Wietse
