Cannot send mail if enabled external mail server

    Hi!


    I have the thing that I can not send mails from user@user1.com to mail@server2.com if:


    user1.com is on srv1.host1.com
    server2.com is on srv1.host1.com and external mail server is on srv2.host1.com


    srv1.host1.com tells me, there is no mail address like mail@server2.com


    I have


    i-mscp 1.3.16
    debian 8.6
    external mail server
    only some plugins, that should not effect mail (like panel redirect and serverdefaultpage)


    Log:



    Code: mail.log
    1. postfix/smtpd[26947]: NOQUEUE: reject: RCPT from 00.00.00.00.wireless.dyn.drei.com[00.00.00.00]: 550 5.1.1 <mail@server2.com>: Recipient address rejected: User unknown in virtual mailbox table; from=<user@user1.com> to=<mail@server2.com> proto=ESMTP helo=<[192.168.2.17]>

    I use external resolving.