Outlook emails not reaching some recipients

Didy Ward 0 Reputation points
2026-11-09T10:19:54.7+00:00

For some time now I have realised that some of my emails are not being delivered to some recipients. This can be directly sent emails or emails to some of the people within a group email. Whether there is an attachment or not makes no difference.

I do not get a 'not delivered' notice and the emails appear in my sent folder. But the recipient cannot find my email in their spam folders and for them it is as if it was never sent.

Can you please tell me how this can be fixed?

Outlook | Windows | Classic Outlook for Windows | For home
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  1. AI answer

    2026-11-09T10:20:16.16+00:00

    If messages appear in Sent Items but some recipients never receive them and no non-delivery report is returned, the most supported fixes are these:

    1. Check the recipient address carefully and resend A bad or outdated recipient entry can cause delivery problems even when the message looks sent.
    2. Remove the recipient from Outlook AutoComplete and type the full address again This is especially relevant if the problem happens when replying or forwarding, or only for certain people.
      • Open a new email.
      • Start typing the recipient name/address.
      • When the suggestion appears, highlight it without selecting it.
      • Select the X next to the suggestion, or press Delete.
      • Type the full email address manually and send again.
    3. If the issue affects only some members of a group email Check whether the addresses shown in the error report or group are correct, and remove any old or invalid addresses from the group.
    4. Ask affected recipients to check whether the message was filtered or redirected For missing group mail or mail that seems to vanish, common causes include:
      • mailbox rules moving or deleting the message
      • the recipient not being a member of the group when the message was sent
      • recent group membership changes not yet fully propagated
      • for Microsoft 365 Groups, members not being subscribed to receive group messages in their inbox
    5. If the recipient uses Outlook.com or another provider and there is still no bounce Common recipient-side causes include:
      • invalid email address
      • recipient mailbox full
      • recipient server issues
      • spam filtering or blocklisting on the recipient side
    6. If a message includes a large attachment, reduce it and resend Outlook.com cannot send attachments larger than 25 MB. Large attachments can also prevent resend options from working in some scenarios.
    7. If the problem is only in classic Outlook on Windows and sending produces an NDR in replies/forwards Update Outlook to the fixed build:
      • Go to File > Office Account > Update Options > Update Now.
      • The reply/forward AutoComplete-related NDR issue was fixed in Version 2403 Build 17425.20146.
    8. If classic Outlook on Windows shows NDR error 0x80040305 This was fixed in later builds, and the workaround is to reduce nested folders to under 500 and keep folders collapsed.

    A practical end-to-end test is:

    • send a plain new message with no attachment to one affected recipient
    • remove and retype that recipient’s address first
    • if sending to a group, verify the member is still in the group and not filtered by a mailbox rule
    • if the recipient still gets nothing, ask that recipient to check server-side filtering, mailbox rules, and whether the mailbox is full
    AI-generated content may be incorrect. Read our transparency notes for more information.

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  2. Emma1-N 14,920 Reputation points Microsoft External Staff Moderator
    2026-11-10T03:46:00.25+00:00

    Welcome Didy Ward,

    Thanks for reaching out to Microsoft Q&A Forum. I understand that some of your emails sent from classic Outlook for Windows don't reach certain recipients, including some members of a group email. You don't get a non-delivery notice, the emails show in your Sent Items folder, and the recipients can't find them, not even in their spam folders.

    To help narrow this down, could you please share:

    • What type of email account do you send from in Outlook (for example Outlook.com/Hotmail, Gmail, or an address from your internet provider)?
    • Do the recipients who miss your emails share a common email provider or domain (for example, all on the same company or provider address)?

    Please make sure you already tried the Q&A Assist steps. In addition, please try the following:

    1, Send a test from the webmail version of your account

    • Sign in to your email account in a web browser (for example outlook.live.com for Outlook.com accounts).
    • Send a short message to one of the affected recipients.
    • If the recipient gets this message, the issue is most likely with the Outlook app on your computer, so continue with the steps below.

    2, Start Outlook in Safe Mode to rule out add-ins

    • Close Outlook.
    • Press Windows key + R, type outlook.exe /safe, and press Enter.
    • Send a test message to an affected recipient.
    • If it arrives, go to File > Options > Add-ins, select COM Add-ins next to Manage, click Go, and turn off add-ins one at a time to find the one causing the problem. Email scanning add-ins from antivirus software are a common cause.

    3, Confirm which account Outlook sends from

    • Open a new email and check the From field.
    • If you have more than one account set up, go to File > Account Settings > Account Settings, select the correct account, and click Set as Default.

    4, Repair the email account

    • Go to File > Account Settings > Account Settings.
    • Select your email account and click Repair.
    • Follow the prompts, then restart Outlook.

    Looking forward to your update.

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