Outlook email delivery seems intermittent, only 7 of 10 emails delivered to test recipient

Question

Outlook email delivery seems intermittent, only 7 of 10 emails delivered to test recipient

Todd Cokinos 0

Spectrum internet service; running Outlook client on PC with Microsoft 365; Have both Spectrum and Outlook email configured in the Outlook client.

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Sent 10 test emails from my Outlook/Exchange account in the Outlook client to both my Spectrum email address and my Outlook email address. All 10 came to the Outlook inbox. Only 7 made it to the Spectrum in box. Spectrum verified all their servers are up and running, and my settings were correct. All testing on the Spectrum side was working fine for multiple emails.

Is there some way to trace or get error logs for these undelivered emails from the Microsoft Outlook side of things? I get no failed delivery notices (these don't seem to occur much these days).

Has anyone seen any intermittent delivery issues out of the Microsoft 365 servers? 70% of deliveries within a 2 minute window is not a good result for me, but I don't know where to start tracking down the failures.

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3 answers

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Answer 1

Hornblower409 18,925

@Todd Cokinos said

Is there some way to trace or get error logs for these undelivered emails from the Microsoft Outlook side of things?

Depends.

If you have a MS 365 Business plan, where you have access to the Exchange Admin panel for your account, please advise and we'll talk about Exchange Online Message Trace.

If not, Classic Outlook Advanced Logging only traces the message to the point where it's accepted by the Microsoft SMTP server. And your Spectrum problem is obviously downstream from there.

get no failed delivery notices (these don't seem to occur much these days).

You should be getting NDRs IF the Spectrum SMTP server rejects the mail. But if Spectrum initially accepts the message and only later filters, quarantines, or otherwise loses it, you don't get anything back.

from my Outlook/Exchange account

1 -- Again, do you have a MS 365 work/business plan that includes an Exchange Online mailbox? Or just a personal outlook.com email account?

2 -- Do the missing mails show if you look directly at the server using Spectrum Web Mail?

3 -- Same if you send from your Outlook account using Outlook Web? https://outlook.cloud.microsoft/

Todd Cokinos 0 Reputation points

2026-11-09T10:58:21.4833333+00:00

Hello. Thank you for replying. My account in indeed a personal Microsoft 365 account, so trace capabilities are easily arrangeable. However, I did find that the 3/10, and then later 4/10, test messages that did not immediately deliver, did in fact deliver anywhere from 5-8 hours later that day. So there was clearly a server bottleneck, or some kind of pending arbitration, or other going on in the "middle ground" where I have no visibility beyond the Advanced Logging. So, I did eventually receive the emails, but they were significantly delayed. To your direct questions, the emails did not show on Spectrum Web Mail, and I did not investigate tests via Outlook web given the message ultimate arrival, but this might be useful information to gather in my next set of tests. Thanks again.
Hornblower409 18,925 Reputation points

2026-11-09T14:10:24.11+00:00

@Todd Cokinos said

This issue can be considered closed. The "missing" emails were eventually delivered

Thank you for the update.

You can still do some detective work, for this incident and if (when?) it happens again.

Look at the Message Headers for one of the delayed items. The "Received:" timestamps, may let you determine where in the delivery path most of the delay occurred.
https://support.microsoft.com/en-gb/outlook/view-internet-message-headers-in-outlook
Todd Cokinos 0 Reputation points

2026-11-09T14:38:31.6433333+00:00

Thanks, yes I dug in deeper into finding the Message Header and am running it through the Message Header Analyzer (microsoft) now too. Thanks.

Answer 2

Chloe-V 15,240 Microsoft External Staff Moderator

Hi @Todd Cokinos

Thank you for providing the detailed test results.

Could you please confirm whether the sending account is a Microsoft 365 Business/Exchange Online account managed by an organization, or a personal Outlook.com account?

This will help us determine whether Message Trace is available to check the delivery status of the missing emails.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Todd Cokinos 0 Reputation points

2026-11-09T11:01:07.46+00:00

Please see above for even further comments, but mine is a personal Outlook.com account so I was unable to trace, just do Advanced Logging, which only confirmed what I could already determine about the primary sends and the final receipts. So errors on the full set of outgoing messages was reported by Adv Logging. Thank you for your reply.

Answer 3

This issue can be considered closed. The "missing" emails were eventually delivered, after 5-8 hours. Blame server delay, some kind of rules/arbitration, or your favorite bottleneck. I could not trace do to be a personal Outlook account connecting to M/S servers, and Advanced Logging showed no errors on the send of the test messages, or anomalies in the receipt of the limited set of messages.

So, I will have to just hope that whatever delays in the "murky middle ground" are limited and will be eventually fixed... since I have no further visibility into the serverer handling in that path of the delivery.