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It sounds like Postini is causing this.<br />
<br />
Ref link:<br />
<a href="https://support.google.com/postini/answer/139512?hl=en" rel="ugc nofollow">https://support.google.com/postini/answer/139512?hl=en</a>
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It sounds like Postini is causing this.

Ref link:
https://support.google.com/postini/answer/139512?hl=en [https://support.google.com/postini/answer/139512?hl=en]

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I understand Postini is causing this. &nbsp;I cannot do anything about someone else's mail server.<br />
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I think there is a setting in exchange that will send the email as separate mail to multiple users at the same domain instead of multiple TO:s. DO you know where this is?
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I understand Postini is causing this.  I cannot do anything about someone else's mail server.

I think there is a setting in exchange that will send the email as separate mail to multiple users at the same domain instead of multiple TO:s. DO you know where this is?

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I am trying to send mail to 2 mail recipients &nbsp;to the same domain. &nbsp;It is failing:<br />
20 Mar 2014 00:12:07 [0x000003ac] - ROUTER: &lt;&lt;&lt;&lt;&nbsp;451 Recipients not all at same mail host - psmtp<br />
20 Mar 2014 00:12:07 [0x000003ac] - ROUTER: Error sending RCPT-To: 451 Recipients not all at same mail host - psmtp (will retry...)<br />
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If I send the mails as two separate mails each mail goes thru.<br />
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I think there is a setting in exchange that will send the email as separate mail to multiple users at the same domain instead of multiple TO:s.
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I am trying to send mail to 2 mail recipients  to the same domain.  It is failing:
20 Mar 2014 00:12:07 [0x000003ac] - ROUTER: <<<< 451 Recipients not all at same mail host - psmtp
20 Mar 2014 00:12:07 [0x000003ac] - ROUTER: Error sending RCPT-To: 451 Recipients not all at same mail host - psmtp (will retry...)

If I send the mails as two separate mails each mail goes thru.

I think there is a setting in exchange that will send the email as separate mail to multiple users at the same domain instead of multiple TO:s.

exchange 2010 451 Recipients not all at same mail host - psmtp

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

Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.

Email Servers

An email client, email reader or more formally mail user agent (MUA) is a computer program used to access and manage a user's email. A web application that provides message management, composition, and reception functions is sometimes also considered an email client, but more commonly referred to as webmail.

Email Software

An email client, email reader or more formally mail user agent (MUA) is a computer program in the category of groupware environments used to access and manage a user's email. A web application that provides message management, composition, and reception functions may internally act as an email client; as a whole, it is commonly referred to as webmail. Likewise, email client may be referred to a piece of computer hardware or software whose primary or most visible role is to work as an email client. Email clients can also have other systems, like calendars, notes and contact managers.