[Dovecot] Dovecot proxy to Microsoft Exchange 2013

[Ricardo Machini Barbosa]

Hello,

I am trying to do a proxy with dovecot to IMAP backend server that are 
using Microsoft Exchange 2013.
I already did this with Microsoft Exchange 2007 and Microsoft Exchange 
2010 and it works perfectly! But with Microsoft Exchange 2013 I can not 
perform LOGIN.

The error log message is:
/imap-login: Error: proxy(user at domain.com.br): Login for 
exchange2013.domain.com.br:143 timed out in state=4 (after 30 secs, 
local=x.x.x.x:59640)/

My troubleshoot was:

- tcpdump on dovecot server side:
     I can see the commands sent/received by Microsoft Exchange. But no 
the "OK LOGIN" response.

/* OK The Microsoft Exchange IMAP4 service in xxxx is ready.//
//C CAPABILITY//
//L LOGIN "user at domain.com.br" "123456"//
//* CAPABILITY IMAP4 IMAP4rev1 AUTH=PLAIN STARTTLS UIDPLUS CHILDREN IDLE 
NAMESPACE LITERAL+//
//C OK CAPABILITY completed./

- tcpdump with telnet login on dovecot server side:
     Works fine.

/* OK The Microsoft Exchange IMAP4 service in xxxx is ready.//
//a login "user at domain.com.br" "123456"//
//a OK LOGIN completed.//
//a logout//
//* BYE Microsoft Exchange Server 2013 IMAP4 server signing off.//
//a OK LOGOUT completed./

- Log verbose on Microsoft Exchange 2013.
     Look like that Microsoft Exchange did not receive the login command.

Someone already tried do this with Microsoft Exchange 2013 ?

See bellow some information about my dovecot configuration:

/# 2.2.2: dovecot.conf//
//# OS: Linux 2.6.32-358.2.1.el6.centos.plus.x86_64 x86_64 CentOS 
release 6.4 (Final)//
//
//base_dir = /var/run/dovecot///
//disable_plaintext_auth = no//
//listen = x.x.x.x//
//mbox_write_locks = fcntl//
//passdb {//
//  args = /etc/dovecot/dovecot-ldap.conf.ext//
//  driver = ldap//
//}//
//
//protocols = imap pop3//
//service imap-login {//
//  inet_listener imap {//
//    port = 143//
//  }//
//  inet_listener imaps {//
//    port = 993//
//    ssl = yes//
//  }//
//  process_min_avail = 4//
//  service_count = 0//
//  vsz_limit = 512 M//
//}//
//service pop3-login {//
//  inet_listener pop3 {//
//    port = 110//
//  }//
//  inet_listener pop3s {//
//    port = 995//
//    ssl = yes//
//  }//
//  process_min_avail = 4//
//  service_count = 0//
//  vsz_limit = 512 M//
//}//
//ssl_cert = </etc/dovecot/certificate/chained.crt//
//ssl_key = </etc/dovecot/certificate/cert.key//
//userdb {//
//  driver = prefetch//
//}//
//
///etc/dovecot/dovecot-ldap.conf.ext//
//hosts = x.x.x.x//
//dn = cn=admin,o=email//
//dnpass = xxxxxxx//
//ldap_version = 3//
//base = o=email//
//scope=subtree//
//pass_filter = mail=%u//
//pass_attrs = uid=user,=password=,=proxy=y,mailHost=host,=nopassword=y/

Thanks,
Ricardo Machini