Apple Mail in 10.7.4 with Mac OS X Server 10.6.8 and Mobile Access Server

I have a IMAP server running on a Mac OS X server 10.6.8. Using the mobile access server I am forwarding port 999 to 993 (my server is behind a firewall that blocks port 993). This configuration was working fine so far.

However, since I updated clients to Mac OS X 10.7.4 I have a problem with Apple Mail (Version 5.2 (1278)). On the server side I get messages like

May 14 07:20:52 apfel com.apple.securityproxy_mail[364]: V1:IMAP:ACCESS[client:xx.xx.xx.xx:52652, proxy:xxx.xx.xx.xx:999,
server:xxxxx.xxxxxxxx.xxxxx.xx:993, connected_secs:180, user:, client-authmethod:, proxy-authmethod:, client-transport:ssl,
server-transport:ssl, state:proxy-connected, result:BAD. User not authorized by proxy server. No valid auth method from client.
Verify that client and server are configured for mobile access. Connection was closed cleanly.]

You see I don’t even get a username or client-authmethod …

With older clients I get

May 14 07:15:52 apfel com.apple.securityproxy_mail[364]: V1:IMAP:ACCESS[client:xx.xx.xx.xx:49577, proxy:xxx.xx.xx.xx:999,
server:xxxxx.xxxxxxxx.xxxxx.xx:993, connected_secs:1, user:xxxxx, client-authmethod:IMAP-LOGIN, proxy-authmethod:CRAM-MD5,
client-transport:ssl, server-transport:ssl, state:server-authorized, result:OK. Connection was closed cleanly.]

If I use other Mail clients on Mac OS X 10.7.4 (e.g. Postbox) then everything works fine. So I strongly believe it is a bug in Apple Mail.

BTW: I already posted my problem on Apple discussions

https://discussions.apple.com/message/18382353#18382353

Does anyone else have this problem?