Untrusted domain between two forest for SQL connection

Here is my topology
Internal domain: inside.local (Two DCs)
DMZ Domain: outside.local (Two DCs)
Inside.local have a Web Application used by the local employees (Application is named  WebApp)
Outside.local, have a database that WebApp uses, its a C# running on IIS on Windows 2012
one-way trust relation, outside.local trust authentication request from inside.local

WebApp needs to connect to the database in the DMZ, but users are getting the following error message.
Error message: Login failed. The login is from an untrusted domain and cannot be used with Integrated authentication.

I try to use ODBC from WebApp Server to connect to the SQL Server in the and I got the same error message.
Note that this issue is not persistent, users may fail in login for about 1 minutes, and then it work fine and they can login and work fine for another 10 minutes, and so on..
I check the authentication protocol and its using NTLM
Any idea on why this may happense
Faris MalaebAsked:
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Vitor MontalvãoMSSQL Senior EngineerCommented:
When working with different domains you'll need first to trust them. You can follow the steps in this link.
After creating the trust between the domain you can now add users from the outside domain into the SQL Server instance logins so they can be able to connect to a database.
Faris MalaebAuthor Commented:
Hi, Thanks for the comment,
There is a one way trust, the Outside.local Trust the inside.local, and authentication request are working fine.
I can login to any server in Outside.local using Inside.local credentials.
Vitor MontalvãoMSSQL Senior EngineerCommented:
I think it should be 2 ways trust as both domains needs to reply back to each other.
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Faris MalaebAuthor Commented:
I enabled Netlogon Logging and I found some strange errors
06/21 11:58:32 [MISC] [688] In control handler (Opcode: 4)
06/21 11:58:34 [LOGON] [18268] SamLogon: Network logon of DOMAIN\Server1$ from Server1 Entered
06/21 11:58:39 [CRITICAL] [18268] NlPrintRpcDebug: Couldn't get EEInfo for I_NetLogonSamLogonEx: 1761 (may be legitimate for 0xc0020017)
06/21 11:58:39 [LOGON] [18268] SamLogon: Network logon of DOMAIN\Server1$ from Server1 Returns 0xC0020017
06/21 11:58:42 [MISC] [688] In control handler (Opcode: 4)
06/21 11:58:50 [LOGON] [18268] SamLogon: Network logon of DOMAIN\user1 from ClientPC1 Entered
06/21 11:58:53 [MISC] [688] In control handler (Opcode: 4)
06/21 11:58:53 [LOGON] [12296] SamLogon: Network logon of DOMAIN\user1 from ClientPC1 Entered
06/21 11:58:55 [CRITICAL] [18268] NlPrintRpcDebug: Couldn't get EEInfo for I_NetLogonSamLogonEx: 1761 (may be legitimate for 0xc0020017)
Vitor MontalvãoMSSQL Senior EngineerCommented:
This is out of my expertise but by the logged error it seems that somebody here already had the issue. Check if the solution provided can help you.
Vitor MontalvãoMSSQL Senior EngineerCommented:
Otherwise check if the account isn't locked out.
Faris MalaebAuthor Commented:
Hi, the trust relationship oneway will be fine, it might be required to be twoway incase of Kerberos authentication.
The accounts are actually not locked out. I confirm that its working fine and no lockout in the history log.
Faris MalaebAuthor Commented:
Hi, I fixed the issue.
I updated the application web.config \ ConnectionString \ Integrated Security
The value was True, I change it to SSPI (Integrated Security=SSPI) and now its working fine.

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Faris MalaebAuthor Commented:
The problem is now fixed and the issue has disappeared.
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