Hello guys!

sorry in advance for the noob question, but I was the second day I can not find a solution. Please help!

I have a domain xn - d1abichgllj9dyd8a.su
Hosted on the providers server where i have a vm with Ubuntu 12.04
hostname - dresden.xn - d1abichgllj9dyd8a.su
it has a static IP
installed Zimbra 8.0.5
set A and MX record

Code:
method:	[unknown]
msg:	try again: Unable to connect to the MTA
code:	mail.TRY_AGAIN
detail:	soap:Receiver
trace:	qtp426168733-156:https://ip:443/service/soap/SendMsgRequest:1387392246510:89863f0a05f571ec
request:	
Body: {
  SendMsgRequest: {
    _jsns: "urn:zimbraMail",
    m: {
      e: [
        // [0]:
        {
          a: "mailuser@mail.com",
          t: "t"
         },
        // [1]:
        {
          a: "admin@dresden.xn--d1abichgllj9dyd8a.su",
          t: "f"
         }
       ],
      idnt: "b13eafa2-3628-44da-8212-c1403c8feaeb",
      mp: [
        // [0]:
        {
          content: {
            _content: "test"
           },
          ct: "text/plain"
         }
       ],
      su: {
        _content: "test"
       }
     },
    suid: 1387392244086
   }
 },
Header: {
  context: {
    _jsns: "urn:zimbra",
    account: {
      _content: "admin@dresden.xn--d1abichgllj9dyd8a.su",
      by: "name"
     },
    authToken: "(removed)",
    notify: {
      seq: 34
     },
    session: {
      _content: 11,
      id: 11
     },
    userAgent: {
      name: "ZimbraWebClient - SAF7 (Mac)",
      version: "8.0.5_GA_5839"
     }
   }
 }
stack:	getResponse@https://xn--d1abichgllj9dyd8a.su/js/Startup1_1_all.js.zgz?v=130910125714:22130:17 _handleResponseSendRequest@https://xn--d1abichgllj9dyd8a.su/js/Startup1_2_all.js.zgz?v=130910125714:22081:16 run@https://xn--d1abichgllj9dyd8a.su/:854:23 _runCallback@https://xn--d1abichgllj9dyd8a.su/js/Startup1_1_all.js.zgz?v=130910125714:21882:15 run@https://xn--d1abichgllj9dyd8a.su/:854:23 __handleResponse@https://xn--d1abichgllj9dyd8a.su/js/Startup1_1_all.js.zgz?v=130910125714:1235:6 onreadystatechange@https://xn--d1abichgllj9dyd8a.su/js/Startup1_1_all.js.zgz?v=130910125714:1175:31