Сервер сообщает об ошибке err server unavailable 21

Recently I entered the dreaded -ERR Server Unavailable. 21 error on an Exchange Server. The strange this was that this did not happen to all mailboxes but only to a couple of mailboxes. Nothing written in the eventlog, just –ERR Server Unavailable. 21 immediately after entering my credentials (this error can be seen when using TELNET to access a mailbox using POP3).

To get more information regarding the login process you can enable POP logging on the CAS Server. Be very careful with this and only enable it for test purposes. If you forget to turn it off most likely your CAS server will shutdown in a couple of days because the system drive is filled up with POP3 log files.

Enable POP logging using the Exchange Management Shell:

Set-POPSettings –ProtocolLogEnabled:$TRUE

And don’t forget to restart the POP3 service.

The POP3 log files are stored in C:\Program Files\Microsoft\Exchange Server\V14\Logging\Pop3. After testing and the Error Server Unavailable. 21 error show up, disable logging (Set-POPSettings –ProtocolLogEnabled:$FALSE), restart the service and open the POP3 log file.

2012-03-08T21:26:02.937Z,0000000000000002,1,127.0.0.1:110,127.0.0.1:24097 ,,0,23,5,user,joe@sixpack.com,R=ok;RpcL=-1;LdapL=-1
2012-03-08T21:26:13.296Z,0000000000000002,2,127.0.0.1:110,127.0.0.1:24097 ,,46,10,29,pass,*****,»R=»»-ERR Server Unavailable. 21″»;RpcL=-1;LdapL=-1;
Msg=User:joe:bf6c873e-4289-4a64-87bf-2ade894947cd:DAG04-MBX05:MBX19.E14.local; Excpt=»»Could not load file or assembly ‘Microsoft.Exchange.Compliance, Version=14.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35’ or one of its dependencies. The system cannot find the file specified.-FileNotFoundException»»»

This turns out to be a bug in the Exchange 2010 setup (even in SP1) where the POP3 config file is not created appropriately. Unfortunately the same is true for IMAP4, but the fix is identical. The config files are called Microsoft.Exchange.Pop3.exe.config and Microsoft.Exchange.Imap4.exe.config and can be found in the directory C:\program files\Microsoft\Exchange Server\V14\ClientAccess\PopImap\

Add the following pieces to the XML file (both POP3 and IMAP4):

<dependentAssembly>
<assemblyIdentity name=»Microsoft.Exchange.Compliance» publicKeyToken=»31bf3856ad364e35″ culture=»neutral» />
<codeBase version=»14.0.0.0″ href=»file:///C:\Program Files\Microsoft\Exchange Server\V14\bin\Microsoft.Exchange.Compliance.dll» />
</dependentAssembly>

image

Restart the POP3 and IMAP4 service and the POP3 Server Unavailable no longer appears.

Microsoft UC Specialist

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I installed a new Exchange 2010 infrastructure which is composed of 4 server.  One of them is Hub Transport and Mailbox, one is Mailbox, one is Client Access and the last one is Edge.  I already migrated over 1200 accounts and everything looks
ok, mail is flowing great, all services and databases up and running, except for the POP3 service.

I already enabled the service to start automatically, configure it to accept plain text login.  This is a requirement because a legacy app that is in use by the organization is using POP3 and won’t accept any other configuration.

I am having the error described in the following thread:

http://social.technet.microsoft.com/Forums/en-US/exchangesvrmigration/thread/1ad1b55e-8cc6-4676-87ee-0a6216f1b399/

The error that I’m receiving is the same:

“-ERR Server Unavailable. 21”

Neither the app or Outlook can be configured to use POP3 successfully.  The error happens when I test the account configuration.  I already tried all settings possible for the configuration of the account.

After checking the solution described in the above link, I made a backup of the pop3.config file, added the lines of code that the user in the forum suggest, restarted the POP and IMAP servicies, but it didn’t solve my problem.  I know IMAP is not necessary
but I enabled it and configured it just in case.

I am using Exchange 2010 SP1 rollup update 4.  Windows Server 2008 R2 is installed on the 4 servers with all updates and patches as of today.

Where else should I look for?  I think my problem is related to what the user stated in the forum, because the file of the POP3 configuration didn’t have the line for «Microsoft.Exchange.Compliance»
etc.

Please, help me in the solution of this problem.

Update:

I activated advanced loggin for the protocol and it seems I have the same problem of the link, but I can’t solve it or I don’t know where to paste the lines of codes.  The error is:

2011-09-19T20:53:53.602Z,000000000000003A,4,10.0.10.82:110,10.0.60.183:4158,,4203,10,29,pass,*****,»R=»»-ERR Server Unavailable. 21″»;RpcC=18;RpcL=171;LdapC=12;LdapL=32;Msg=»»User:migrationadmin:4c215846-c7a5-43f9-a931-63a5af018f37:Mailbox Database Server1
DB1:EXCHANGESRV01.contoso.com»»;Excpt=»»Could not load file or assembly ‘Microsoft.Exchange.Compliance, Version=14.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35’ or one of its dependencies. The system cannot find the file specified.-FileNotFoundException»»»

Please note I changed some info about our domain.

Thanks in advance,

Jose Angel Rivera

  • Изменено

    20 сентября 2011 г. 0:03

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I run Exchange 2008 on my SBS 2008 server.  I use POP3 to log in remotely to check my email with Outlook 2010.

All has been running well and then all of a sudden without touching anything on the server or the netbook Outlook fails to connect to the SBS2008 Exchange server and returns the following message after asking my for my user and password:-
! Task ‘Home POP3 Server — Receiving’ reported error (0x800CCC92): Your e-mail server rejected your login.  Verify your user name and password for this account in Accounting Settings.  The server responded : -ERR Server Unavailable. 21′

«Home POP3 Server’ is the name of my account.

So I have tried TELNET ie
TELNET
OPEN server 110
and then I submit by user code and password with USER and PASS COMMANDS and it responds with the following messages:-
-ERR Server Unavailable. 21
-ERR Connection is closed. 22

I have tried restarting the Server — still there.
I have looked at the services running — everything seems to be fine.

Any ideas????

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  • Question

  • Hello, 

    POP3 service on the Exchange 2013 version of CU5 913.22 does not work. just stopped working, but do not know when as yet not launched it productively. 
    I get an error in Outlook when connecting to or through Telnet during the «list». 
    POP3 service is running on the backend servers. 
    User has enabled POP3 mailbox. 
    Connectory are set to default-path. 
    Firewall allows traffic between Cas server and Mailbox server. 
    Exchange is published by Kemp. All real servers, certificates are added. 

    Met up with this version of this error? The net information regarding 2010 and adding an entry to the configuration file pop3, but in 2013 the ex has this entry. 

    Please help.

    Regards Lukas

Answers

  • Hi,

    Certificate was a problem on one of mailbox server. When i shutdown failover mailbox server, POP3 worked correctly.

    I need to figure out how to solve this problem.

    BR/Lukas

    Problem solved by editing Certificate to use in service POP and SMTP. strange because it worked. and no one moved these options …

    • Edited by

      Wednesday, August 13, 2014 11:04 AM
      solved

    • Marked as answer by
      Niko.Cheng
      Thursday, August 14, 2014 6:29 AM

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eM Client

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