[imp] How to include FQDN in HELO?

[Howard Ong]

I got Horde/Imp running on Windows. I have just changed ISP and did some reconfiguration. IMAP works fine with the new mail server, but sending email gives me a:
 
Failed to add recipient: henry.oliver at azma.com.au [SMTP: Invalid response code received from server (code: 550, response: <localhost>: Helo command rejected: Invalid HELO)]

This seems to be caused by the mail server not accepting a "HELO localhost" command. I need to configure Horde/IMP to send a "HELO azma.com.au" instead. How do I do that?

I tried changing the "primary DNS suffix" in Windows, but that makes it worse: I can't even log in after the change.

Extracts of selected config file below. Apprecite any help.

Imp's servers.php:
$servers['imap'] = array(
    'name' => 'mail.westnet.com.au',
    'server' => 'mail.westnet.com.au',
    'hordeauth' => false,
    'protocol' => 'imap',
    'port' => 143,
    'folders' => '',
    'namespace' => '',
    'maildomain' => 'aurora-consult.com.au',
    'smtphost' => 'mail.westnet.com.au',
    'smtpport' => 25,
    'realm' => '',
    'preferred' => true,
    'dotfiles' => false,
    'hierarchies' => array()
);

Horde's conf.php:
$conf['mailer']['params']['host'] = 'mail.westnet.com.au';
$conf['mailer']['params']['auth'] = '0';
$conf['mailer']['type'] = 'smtp';


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