Outlook showing emails 'sent' but not received by recipients

This issue has been happening to me, intermittently for over a year. It's just happened again this week so clearly the issue isn't fixed.

I have the exact same problem. I have no idea where these emails disappear to. Outlook does not provide any error messages. My email is in the "sent" folder. The reciepient is a person to whom I send many emails. Most are received. Periodically, they are not. I have put in place the following temporary solution.
I have another email account in gmail. I always cc my emails to this account as well sending to my recipient.
After sending the email, I check my gmail account to see if it has been received.
If it has not been received in my gmail account, I check with the recipient to see if he has received my email. !00% of the time he has not received it.
I use my gmail account to send the email with exactly the same contents and subject line. I also cc my outlook account. The email is received by both the recipient and in my outlook account.

I do believe that there is a bug in outlook which periodic. It only happens occasionally. So now, I always cc myself on my other account to be sure that an email is received by the repicient(s).

I have what seems to be exactly the same problem: When I send an email, it shows up under "Sent Items", but doesn't reach the recipient. I don't get any message of failed delivery or any other error message. I've even tried sending test emails to myself (the same email address), with the same result - appearance under "Sent Items", but not in the Inbox. It doesn't appear under "Junk" either.

As far as I can tell, I can still receive emails from others just fine.

For me the problem started sometime in the last 24 hours. As far as I know, I have not experienced this problem before. For reference, I'm using outlook.live.com in my browser.

Hi Samet Greetings! Thank you for posting on Microsoft Community. I will be happy to help. I am a user just like you and only trying to advice/ assist in a best possible way I could resolve your issue. I understand your concern with the email delivery issue you're experiencing. It's understandably especially concerning when important emails like job applications and responses reaching the recipient. Here are some things you can try to diagnose and hopefully resolve the problem: 1. Identify the root cause: Check your email provider: Contact your email provider, whether it's your business email provider or Hotmail, and inquire about any potential server issues or outages that might be impacting delivery. Review account settings: Double-check your sending and receiving settings for both accounts. Ensure everything is correctly configured and aligned with your email server settings. Analyze email headers: Use a tool like MXToolbox or Email Header Analyzer to examine the email headers of your undelivered emails. This can reveal technical details like spam scoring and routing information that might indicate the reasons for non-delivery. Disclaimer: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it. Check recipient's spam folder: Ask the recipients you haven't heard back from to check their spam folder, just in case your email landed there by mistake. 2. Address potential triggers: Content review: Analyze the content of your emails that haven't been delivered. Avoid excessive capitalization, exclamation marks, or phrases commonly flagged by spam filters. Sender reputation: Check your domain and sending IP address's reputation using tools like SenderScore or Talos Intelligence. Address any negative reputation issues that might be impacting deliverability. Blacklisting: Use MXToolbox or another blacklist checker to ensure your domain and IP address are not listed on any major blacklists. Disclaimer: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.** 3. Implement solutions: Improve authentication: Double-check your SPF, DKIM, and DMARC records for both email accounts. Ensure they are valid, aligned, and properly configured in your DNS settings. Warm-up new IP addresses: If you're using a new IP address for sending emails, gradually increase the volume to establish a positive reputation with email servers. Contact recipient's email provider: If your emails consistently bounce for specific recipients, try contacting their email provider directly to inquire about potential delivery blocks or filtering rules. 4. Consider alternative solutions: Temporary email alias: While resolving the issue, consider using a temporary email alias service for important communications to avoid delays. Follow up through other channels: In critical situations where email delivery is unreliable, try reaching out to the recipient through phone calls, LinkedIn messages, or other communication channels. By using the steps above and working with your email providers and recipients, you should be able to identify the root cause and implement solutions to ensure reliable email delivery moving forward. I hope this helps! Don't hesitate to ask if you have any further questions or need additional assistance. Give back to the Community. Help the next person who has this issue by indicating if this reply solved your problem. Click Yes or No below. Kind Regards -Adedayo

I appreciate your response.

I am talking about a technical issue here. I am using my personal email account everywhere, which has the extension msn.com. When I send an email from this account to another person whose account has the extension hotmail.com, my email consistently doesn't reach the recipient. It doesn't even go to the junk or spam folder. This happens intermittently and repeatedly, not just an isolated incident. When I send the same email via Gmail, it is delivered instantly to the recipient. And you are telling me to "Double-check your SPF, DKIM, and DMARC." WHY???

I also have the same problem since 9th April 2024