SOAP server returns error for email subscription-request from an email addr that is shared by more than one contact.

If someone sends a "subscribe" request email from an email address that corresponds to more than one CiviCRM contact:

1) the SOAP server responds with an html "error" page, not with a SOAP error message. This generates an error in the SOAP client - which is expecting an XML response. (We are using the imap2soap.pl script, which is calling the SOAP server's "mailer_event_subscribe" function when the error occurs).

2) There shouldn't really be an error anyhow, since CiviCRM's default Duplicate Matching Rule is that contacts must have at least ONE of email, firstname, lastname to be different. ie. Duplicate email addresses are allowed in CiviCRM.

Note that:

• this is very similar to issue CRM-1495. (http://issues.civicrm.org/jira/browse/CRM-1495)
• this is my first time posting here-- I hope I'm doing things right...
• we are running CiviCRM v1.5, rev7222. I haven't tested this against different versions.

The <body> of the html page served back is:

<body>

<div id="crm-container" lang="en" xml:lang="en">

<div class="messages status">
<dl>
<dt><img src="http://www.xxxx.com//modules/civicrm/i/Error.gif" alt="unrecoverable error" /></dt>
<dd>
Sorry. A non-recoverable error has occurred. <p>19,89 is not of the type Integer</p>
<p><a href="http://www.xxxx.com/" title="Main Menu">Return to CiviCRM menu.</a></p>
</dd>
</dl>
</div>

</div>
</body>