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Hi.<br />
<br />
I've a Exchange 2010 Server that is back to ISA Server 2006. I'va published the OWA, POP3 and Mail Server with no problems. Receive and send e-mails works fine if the Outlook is configured inside office and OWA works fine. But I need configure some machines with POP3 and SMTP. The POP3 connection works and users can receive emails but when they try to send always receive a message<br />
<br />
Server error: '550 5.7.1 Unable to relay'<br />
<br />
If they use in mail client the SMTP configuration with no authentication receive the message, if use a authentication the mail client enter into loop requesting the credentials but never accept. I try using DOMAIN\User, user@internetdomain.com, user@internaldomian.com and never works.<br />
<br />
My IT environment is:<br />
<br />
1 Domain Controller W2K8 R2<br />
1 Excgange 2010 Mx, CAS and HUB in W2K8 R2<br />
1 Exchange 2010 Edge in W2K8 R2<br />
1 ISA Server 2006 SP 1 in W2K3 R2<br />
<br />
Some information will be helpful.
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Hi.

I've a Exchange 2010 Server that is back to ISA Server 2006. I'va published the OWA, POP3 and Mail Server with no problems. Receive and send e-mails works fine if the Outlook is configured inside office and OWA works fine. But I need configure some machines with POP3 and SMTP. The POP3 connection works and users can receive emails but when they try to send always receive a message

Server error: '550 5.7.1 Unable to relay'

If they use in mail client the SMTP configuration with no authentication receive the message, if use a authentication the mail client enter into loop requesting the credentials but never accept. I try using DOMAIN\User, user@internetdomain.com, user@internaldomian.com and never works.

My IT environment is:

1 Domain Controller W2K8 R2
1 Excgange 2010 Mx, CAS and HUB in W2K8 R2
1 Exchange 2010 Edge in W2K8 R2
1 ISA Server 2006 SP 1 in W2K3 R2

Some information will be helpful.

Exchange 2010 SMTP response Server error: '550 5.7.1 Unable to relay'

Interactions between email servers and clients are governed by email protocols. The three most common email protocols are POP, IMAP and MAPI. Most email software operates under one of these (and many products support more than one).  The correct protocol must be selected, and correctly configured, if you want your email account to work.

Email Protocols

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.

Exchange

Microsoft Forefront, formerly known as Internet Security and Acceleration Server (ISA Server), is a network router, firewall, antivirus program, VPN server and web cache that runs on Windows servers. It includes identity management and protection systems, and discontinued systems for threat management and network protection, along with protection for Sharepoint and Exchange. The scope of discussions includes forward and reverse proxy, application and service publishing, virtual private networks (VPNs), outbound access rules, SSL certificates and network routing within either a single node or an highly-available array pairing.