5.1 0 Unknown Address Error 550 Verification Failed For Easy Fix Solution

Some of our users seem to have a known bug with unknown address error 5.1 0 550, validation failed. This problem can occur for many reasons. Now let’s discuss some of them.

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    Target mail server when building version 5.1. 0 will not accept messages from you (the sender), most likely messages for the recipient. This can happen when messages from you (your email address, your Exchange Online organization, or even Exchange Online in general) are blocked by recipient type.

    It’s annoying to get an error message after sending an incoming message. This article describes what to do if you’re experiencing error codes 550 5.1.1 through 5.1.20 appearing in an NDR (also known as an NDR, message, NDR, or DSN).

    I Received This Return Message. How To Solve This Problem In General?

    How do I fix Error 550?

    Check your email address for typos.Check when mail IP is blacklisted.Try forwarding the email in a few days.Try changing your outgoing mail.Check if IP filtering is enabled.Enable SMTP authentication.Fix the SSL method.Contact your Internet Service Provider.

    Here are a few steps you can take.Be yourself.

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  • If the steps in this section don’t resolve your issue, please contact your email administrator and review the information in this article so they can try to resolve the issue you’re experiencing.

    Solution 1: Verify The Recipient’s Email Address

    Sounds simple enough, but a bad email address is the most common problem, often causing 5.1.x errors. Check your punctuation and resend your message immediately if you find a mistake in your email address.

    For more information about resending an Outlook message, see Resending a Netmail message.

    Solution 2: Remove The Recipient’s Email Address From The Autocomplete List

    You may have an invalid entry in the autocomplete list (called the alias cache) for the recipient. For example, the recipient might have moved from an on-premises Exchange service provider to an Exchange or network, and vice versa. Although the recipient’s email address is the same as ours, other internal ideasThe recipient identifiers may have been changed, which will remove your cached entry for the recipient.

    Fix AutoComplete list items in Outlook

    To remove invalid recipients or all recipients from the AutoComplete list in Outlook 2010 later, see Using AutoComplete to Handle Suggested Recipients in To, Cc, and Bcc Fields.

    Fix store list autocomplete in Outlook on these websites

    To remove AutoComplete recipients from the list in Outlook Worldwide (formerly known as Outlook Web App), you can do one of the following:

    Remove Individual Recipients from the Outlook AutoComplete List Associated with a Web List
    1. In Outlook on the web, click New Message.

    2. Start typing the recipient’s name or email URL in the “To” field until the general recipient appears in the drop-down list.

      5.1 0 unknown address error 550 verification failed for

      Screenshot showing the option to send after an email. In our 'Resend' field, the autofill quality returns the email address  Recipient based on the first letters of the recipient's name.

    3. Use the up and down arrow keys to select a recipient, then press Delete.

    Remove almost all recipients from your Outlook, I would say web autocomplete list**

    How do you fix 550 5.1 1 The email account that you tried to reach does not exist?

    Special Solution: Confirm Recipient’s Email Address It sounds too simple, but a completely wrong email address is the most well-known problem affecting 5.1. x problems. If you encounter an error on the first page of an email, check the spelling and retype the message. To resend a message in Outlook, see Resend an email message.

    You can only delete your AutoComplete list in the Luminescent version of Outlook Online. To open a mailbox in a special light version of Outlook on the current website, do one of the following:

  • Open your mailbox in an older web browser that only supports the basic light version of Outlook on the web (such as Internet Explorer 9).

  • 5.1 0 unknown address error 550 verification failed for

    Set up your Outlook on the web to use only a slight modification of Outlook on the web (the change will take effect the next time you open your mailbox):

    1. In Outlook on the web, click Options .

    2. In the ‘Search All Options’ box, type Bright and select a website version from the results.

    3. On the web that opens in search engines, select Use Outlook Premium, then click Save.

    4. Log out, close your web browser completely, and reopen this mailbox in Outlook on this particular website.

  • With your mailbox open in Outlook on the web, follow these steps to remove all entries from the AutoComplete list:

    1. Select options and make sure message is selected.

    2. In the Email Name Resolution section, click Clear Recent Recipients List, then click OK to confirm the dialog box.

    3. How do you fix 550 this message was classified as spam and may not be delivered?

      Often this is due to the fact that SMTP authentication is undoubtedly enabled in these Outlooks. You need to make sure that SMTP authentication is enabled in Outlook and the username is your primary email address along with the account information for your email account.

      While you can switch back to the full version associated with Outlook on the web, switch to the medium version of Outlook, uncheck “Use light version” and click “Save”.


    4. Logging in and out of a web browser. The next time you open your mailbox in a specific supported web browser, you will be using the full version of Outlook on the web.

    To subsequently remove invalid recipients or all recipients from the AutoComplete list in Outlook 2010, see Handling people suggested in the To, Cc, and Bcc fields, with With autocomplete.

    Solution 3: Make Sure The Recipient Won’t Automatically Forward Your Information To Another (usually Invalid) Email Address

    What does 550 envelope blocked mean?

    550 Lock Error or 550 Requested Action Failed: Mailbox Not Available – This is always an SMTP error code. Simply put, this email means that the email you moved was blocked by the recipient’s mail hosting server and forwarded to .

    Does the recipient’s email address in the original message match the recipient’s email address during the NDR? Compare the email address of the recipient in the NDR with the email address of any recipient in the message you receive in your Sent Items folder.

    If specific addresses don’t match, contact them by phone (by phone, in person, etc.) and ask them, even if they’ve set up an email rule that forwards incoming messages from you to someone else. Your period may be trying to send a copy of your feelings to the wrong email address. If the recipient has such a lead, they should fix the email address or remove the shared policy to prevent misdelivery in 5.1.x themes.

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