Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

The host name use is the same one as your machine will report 
if you run ipconfig /all (Host Name value).

Ok now I'm confuzed.

* smtp requires helo to send fqdn and not just the hostname (it's stated somewhere in the rfc's)
* windows xp fqdn is what the computer reports as "full computer name" (at least so does some say, see http://www.ima.com/support/regprob.html)
* a windows xp joined to a domain (a) does not give you any choice about the hostname, it's the computer name which is obviously not fqdn and (b) does report the correct name as "full computer name"
* on linux it works correctly (not using hostname but hostname -f value which is the fqdn)

So at this point it's basically "I cannot send mail from xp to an unforgiving mail server and yes it's a feature so I have to live with it"

Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

The windows XP "feature" for domain name resolution 
apparently gives out a bogus answer. This is an XP bug, 
not a PHP bug. Additionally, "trashcan2.intranet" is not 
a FQDN. See: <http://en.wikipedia.org/wiki/FQDN>.

It seems it's not enough to just gethostname. You have to do something like this (this is not actual production code):

hostent *hent;
gethostname(hname, sizeof(hname));
hent = gethostbyname(hname);
strcpy(hostname, hent->h_name); // h_name is the official name according to winsock api

Reopen, seems to be still valid.

This isn't really a bug in Windows, since the official documentation for Winsock[1] clearly states that the name returned by gethostname "can be a simple host name, or it can be a fully qualified domain name."  Like many parts of Winsock, this is slightly different from the typical behaviour of the POSIX function of the same name, which usually returns a FQDN.

Actually, while the name returned by gethostname() is *usually* a FQDN on a POSIX machine, I don't actually think it's guaranteed there, either.

For a C solution, the code given by danb1974 should work.  An easy way to do it in pure PHP is, instead of just calling gethostname(), call gethostbyaddr(gethostbyname(gethostname())).

Thanks,

-Rick-

[1] http://msdn.microsoft.com/en-us/library/ms738527(VS.85).aspx

Patch available at:
http://php.tuxxedo.net/patches/bugs/38091.patch

This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.

Temporary re-opened, as a reminder to cleanup the POSIX code in sendmail, the bug itself is fixed but the report will remain open until its converted