Exchange SMTP problem

we are using an email proxy and when we get email from out of the company we get the following error and there is no error with local sendings

what should be the problem symptoms like given below

2014-12-20T13:30:44.623Z,POSTA\Default Frontend POSTA,08D1EA65A018C370,52,185.9.157.14:25,185.9.157.13:52871,<,DATA,
2014-12-20T13:30:44.623Z,POSTA\Default Frontend POSTA,08D1EA65A018C370,53,185.9.157.14:25,185.9.157.13:52871,*,SMTPSubmit SMTPAcceptAnySender SMTPAcceptAuthoritativeDomainSender AcceptRoutingHeaders,Set Session Permissions
2014-12-20T13:30:44.623Z,POSTA\Default Frontend POSTA,08D1EA65A018C370,54,185.9.157.14:25,185.9.157.13:52871,>,250 2.1.0 Sender OK,
2014-12-20T13:30:44.623Z,POSTA\Default Frontend POSTA,08D1EA65A018C370,55,185.9.157.14:25,185.9.157.13:52871,>,250 2.1.5 Recipient OK,
2014-12-20T13:30:44.623Z,POSTA\Default Frontend POSTA,08D1EA65A018C370,56,185.9.157.14:25,185.9.157.13:52871,>,354 Start mail input; end with <CRLF>.<CRLF>,
2014-12-20T13:30:44.623Z,POSTA\Default Frontend POSTA,08D1EA65A018C370,57,185.9.157.14:25,185.9.157.13:52871,*,,Proxy destination(s) obtained from OnProxyInboundMessage event
2014-12-20T13:30:44.623Z,POSTA\Default Frontend POSTA,08D1EA65A018C370,58,185.9.157.14:25,185.9.157.13:52871,*,,NextHopFqdn property is null or whitespace when creating InboundProxyLayer
2014-12-20T13:30:54.888Z,POSTA\Default Frontend POSTA,08D1EA65A018C370,59,185.9.157.14:25,185.9.157.13:52871,*,,"Message or connection acked with status Retry and response 451 4.4.0 Primary target IP address responded with: ""454 4.7.0 Temporary authentication failure."" Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts. The last endpoint attempted was 2002:b909:9d0e::b909:9d0e:2525"
2014-12-20T13:30:54.888Z,POSTA\Default Frontend POSTA,08D1EA65A018C370,60,185.9.157.14:25,185.9.157.13:52871,>,451 4.7.0 Temporary server error. Please try again later. PRX4 ,
2014-12-20T13:30:54.888Z,POSTA\Default Frontend POSTA,08D1EA65A018C370,61,185.9.157.14:25,185.9.157.13:52871,<,QUIT,

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PS C:\Users\administrator.SPD> repadmin /showreps
LDAP error 81 (Server Down) Win32 Err 58.
PS C:\Users\administrator.SPD> repadmin /showreps
LDAP error 81 (Server Down) Win32 Err 58.
PS C:\Users\administrator.SPD> DCDIAG /V

Directory Server Diagnosis

Performing initial setup:
   Trying to find home server...
   * Verifying that the local machine posta, is a Directory Server.
   ***Error: posta is not a Directory Server.  Must specify /s:<Directory Server> or  /n:<Naming Context> or nothing to
   use the local machine.
   ERROR: Could not find home server.

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