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check that you are not blacklisted
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It sounds like an SPF issue where the sending domain has setup SPF incorrectly and is not sending from the IP Addresses they have listed in their SPF record.
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It sounds like an SPF issue where the sending domain has setup SPF incorrectly and is not sending from the IP Addresses they have listed in their SPF record.

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Hey guys and gals,<br />
<br />
I have no problems sending email to a particular contact - we'll call their domain 'contoso.com'. &nbsp;However, when they reply to me, they get a kickback saying &quot;&lt;me@mycompany.com&gt;: 550 Validating Sender: domain of user15@contoso.com does not designate xxx.xx.xxx.xx as permitted sender&quot;<br />
<br />
My company uses an internally hosted Exchange 2007 box, and the error being generated does not appear to be coming from Exchange. &nbsp;I've been trying to find a solution to this here and on other sites but not a lot of the replies seem to make a lot of sense or point to any particular solutions. &nbsp;Long story short, my question is this - is this an error on my end (the recipient) or is this an error on the sender's side? If the latter rather than the former, is there a particular article or fix I can pass along to them, since they are convinced it's on my end?<br />
<br />
Thanks!
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Hey guys and gals,

I have no problems sending email to a particular contact - we'll call their domain 'contoso.com'.  However, when they reply to me, they get a kickback saying "<me@mycompany.com>: 550 Validating Sender: domain of user15@contoso.com does not designate xxx.xx.xxx.xx as permitted sender"

My company uses an internally hosted Exchange 2007 box, and the error being generated does not appear to be coming from Exchange.  I've been trying to find a solution to this here and on other sites but not a lot of the replies seem to make a lot of sense or point to any particular solutions.  Long story short, my question is this - is this an error on my end (the recipient) or is this an error on the sender's side? If the latter rather than the former, is there a particular article or fix I can pass along to them, since they are convinced it's on my end?

Thanks!

Can't receive email from one particular domain: &quot;does not designate (IP) as permitted sender&quot;

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

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.

Can't receive email from one particular domain: &quot;does not designate (IP) as permitted sender&quot;

Can't receive email from one particular domain: "does not designate (IP) as permitted sender"