Here's the login request that our webclient sends. Notice your urn is wrong.
Code:
<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope">
<soap:Header>
<context xmlns="urn:zimbra"></context>
</soap:Header>
<soap:Body>
<AuthRequest xmlns="urn:zimbraAccount">
<account by="name">user1</account>
<password>test123</password>
</AuthRequest>
</soap:Body>
</soap:Envelope>