How To Solve The Problem With The Error Message That The Mailbox Is Not Available

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    In this guide, we will learn about some of the possible causes that can lead to the “Mailbox unavailable” error message, and then I will suggest several possible solutions that you can use to try to resolve this issue. If your message looks fake on the recipient’s mail server, one of the ways the servers won’t send you is “Mailbox unavailable.” They do not think that “this is spam” on purpose to give spammers an idea of ​​how to bypass filters. Try to rephrase anything that could be misinterpreted due to spamming.

    Not The Answer You Want? Browse Other Provided Questions About C # Smtpclient Or Ask Your Own Personal Question.

    What does requested action not taken mailbox unavailable mean?

    550 Blocked or possible error 550 Z Requested action not taken: Mailbox unavailable – this is an SMTP error code. Simply put, our message means that the emails sent to customers have been blocked by the recipient’s email server and have been delivered to you.

    The default configuration for many SMTP servers prevents leakage to surrounding domains from an untrusted source. For example, imagine you are accessing the SMTP server for and ask him to send a specific message to [email protected]. Since the SMTP server doesn’t really know who we are, it refuses to forward the message. If the server does this for you, it could potentially be viewed as an open relay, where spammers often do their own thing.

    If you contacted the delivery server and asked them to write an email to [email protected], you may be able to do so. It depends on whether they trust you with who you are talking to. Typically, the server will try to do a reverse DNS lookup and refuse to send email if the IP address you send does not match the IP address of the MX record in the internal DNS. Therefore, if you say why you are the email address of the server, but your IP address does not uniquely match the MX record of, delivery of that particular message will be denied.

    Why am I getting mail delivery failed returning message to sender?

    You are emailing someone. In any case, the most common reason that the “Mail Delivery Failed: Message From Sender” message is not showing up on your web portal is because the provider you are sending email to through your website mistakenly thinks your email spam mail.

    You need to talk to the boss of that SMTP server to get the authentication information so that this method can pass it on for you. You will need to provide these credentials when accessing the SMTP server. Usually thismaybe username / password, maybe windows permissions. It depends on the server and its actual configuration.

    For a great example of submitting feedback, see Unable to Send Email to Send to External Domain Using SMTP.

    How do I fix a 550 error?

    Check your email address for typos.Make sure the IP address of the email is blacklisted.Try to forward the letter after a while.Try changing the output of outgoing emails.Check if IP filtering is possible.Enable SMTP Authentication.Troubleshoot SSL method.Contact your internet service provider.

    substituted on Mar 30 ’13 at 13:25

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    I have been using Windows Server 2012 as a hosting for a long time and after a few years it has worked great. In response, I added public IP coverage for the server to enable Windows Relays and Integrated Windows Authentication.

    Close the dialog and click the Authentication button.

    mailbox unavailable error message

    answered Apr 19 ’15 at 2:56

    mailbox unavailable error message


    We had this problem. everything is still in place in terms of permissions and security.

    After fiddling around in a haystack for a long time. The problem was with several heuristics. In the body of the email, whenever a specific mailbox address was specified, the above error message regarding server change was displayed.

    It took me 2 days like crazy and I was pulling my hair out to find out.

    So, when you’ve got this all figured out, replace the email address in the body of the message with “test” promises. If your email is fine after that, you have a small issue with the heuristic spam filtering we are involved in

    answered March 30, 15 at 17:20

    How do I fix undeliverable email?

    Try this automatic repair: make sure the recipient’s address is indeed valid. Reduce the number of users in the post. If you encounter this error when submitting a project using Outlook or another mobile mail app, use to send a new message.


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