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I've been pulled on other projects so I'll close this question for now. &nbsp;Thanks.<br />

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I've been pulled on other projects so I'll close this question for now.  Thanks.


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Our CEO sent an email and the recipient, upon opening the email, was given a pop-up window that says &quot;Authentication Required&quot;. &nbsp;I've seen this occasionally with internal mail but not with outgoing mail. &nbsp;We also have &quot;Exclaimer&quot; software running on our system. &nbsp;The attached pdf shows the window...<br />
<a href="https://filedb.experts-exchange.com/incoming/2008/11_w45/75068/ARemail.pdf" target="_blank" class="file-inline" title="popup window on recipient's computer... (531 KB)"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path d="M67.508 468.467c-58.005-58.013-58.016-151.92 0-209.943l225.011-225.04c44.643-44.645 117.279-44.645 161.92 0 44.743 44.749 44.753 117.186 0 161.944l-189.465 189.49c-31.41 31.413-82.518 31.412-113.926.001-31.479-31.482-31.49-82.453 0-113.944L311.51 110.491c4.687-4.687 12.286-4.687 16.972 0l16.967 16.971c4.685 4.686 4.685 12.283 0 16.969L184.983 304.917c-12.724 12.724-12.73 33.328 0 46.058 12.696 12.697 33.356 12.699 46.054-.001l189.465-189.489c25.987-25.989 25.994-68.06.001-94.056-25.931-25.934-68.119-25.932-94.049 0l-225.01 225.039c-39.249 39.252-39.258 102.795-.001 142.057 39.285 39.29 102.885 39.287 142.162-.028A739446.174 739446.174 0 0 1 439.497 238.49c4.686-4.687 12.282-4.684 16.969.004l16.967 16.971c4.685 4.686 4.689 12.279.004 16.965a755654.128 755654.128 0 0 0-195.881 195.996c-58.034 58.092-152.004 58.093-210.048.041z"/></svg>ARemail.pdf</a>
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ARemail.pdf

Our CEO sent an email and the recipient, upon opening the email, was given a pop-up window that says "Authentication Required".  I've seen this occasionally with internal mail but not with outgoing mail.  We also have "Exclaimer" software running on our system.  The attached pdf shows the window...

Why does this window &quot;Authentication Required&quot; appear when an external recipient opens an email sent from our exchange 2003 server?

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.

Why does this window &quot;Authentication Required&quot; appear when an external recipient opens an email sent from our exchange 2003 server?

Why does this window "Authentication Required" appear when an external recipient opens an email sent from our exchange 2003 server?