PHP mail() on Server2003 Uses Odd Ports

[Tim Tyler]

Windows Server2003
IIS SMTP Installed
PHP VERSION: 4.3.3

Using Invision Power Board

Mail sent from the IPB using PHP mail() ... (which is configured in php.ini
to use myExternal.MailServer.com) seems to communicate using various ports
in the 1190-1199 range. Here's a clip from a recent email header:

Received: from MyWebServer (xxx.xxx.xxx.95:1199)
by myDomain.com with [XMail 1.16 (Win32/Ix86) ESMTP Server]
id <S13BB47> for <ti*@myDomain.com> from <ph*@myDomain.com>;

The ph*@xxx.com is the default sender address in the php.ini file.

Can anyone tell me why it's using the odd port numbers, and if that's OK? I
suspect it's because IIS SMTP is using port25 on all server IP's. If so,
should I configure things differently? The mail still goes through.

Thx.