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Sending' reported error (0x800CCC78) : 'Cannot send The server responded: 555 5.5.4 Unsupported option: SMTPUTF8'

Anonymous
2025-04-04T14:05:45+00:00

Hi there, any idea to fix that?

"Task 'Janosch Rixius - Sending' reported error (0x800CCC78) : 'Cannot send the message. Verify the email address in your account properties. The server responded: 555 5.5.4 Unsupported option: SMTPUTF8'"

Outlook | Windows | Classic Outlook for Windows | For business

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  1. Anonymous
    2025-04-06T16:15:03+00:00

    Hi Forry.F,

    Thank you for reaching out. :) In the meanwhile, I have fixed issue with my Hosting-provider.

    But I do have other question reading Outlook Windows too.

    Could I ask you these, or shall I post a new question/request in the comm?

    Best,

    Janosch

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  2. Anonymous
    2025-04-10T15:52:51+00:00

    Hey Forry.F

    are you still there?

    I do have other questions reading Outlook Windows too.

    Could I ask you these, or shall I post a new question/request in the comm?

    Best,

    Janosch

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  3. Anonymous
    2025-04-05T10:01:52+00:00

    Hello  Janosch Rixius

    Welcome to Microsoft Community.

    I understand that you encountered the error '555 5.5.4 Unsupported option: SMTPUTF8' when sending emails.

    In order to better understand your problem, I would like to get some more detailed information from you:

    1. Which email providers are your sender and recipient from? Do they support the use of SMTPUTF8 for email names in email interactions?
    2. Try to send emails from your email provider's web page to check whether it can be sent normally, so as to locate whether the problem occurs in the account itself or in the software.
    3. Are your other emails sent normally? Is it only a special contact email that is sent abnormally?
    4. According to the search, SMTPUTF8 often indicates that UTF-8 encoding is allowed in the email name and header fields. Does the email address in the email contain special unrecognizable characters? Some characters look roughly the same, such as full-width and half-width, try to manually re-enter the recipient's email address and then send it.

    Looking forward to your follow-up reply, thank you for your understanding and support.

    Sincere greetings

    Forry.F - MSFT | Microsoft Community Support Specialist

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