Have you checked the sent folder of the account being used to send the flows? If the e-mails are in the send folder, you should ask the recipients to check their spam folders or other folders where a rule may have moved the message.
If the send e-mail action is not failing and showing success, that would indicate that it successfully transmitted the message to exchange. You can look at a flow run and open the outputs of the e-mail action to see if it returns a 200 response.
When you open it, it will show JSON code such as this. If the status code shows something other than 200 on ones that do not send, please share what is returned as it will most likely include some error information. If it shows 200, you’ll need your Exchange team to investigate further. They can run a message trace to see if the message was delivered, blocked, or quarantined.
{
"statusCode": 200,
"headers": {
"Cache-Control": "no-store, no-cache",
"Pragma": "no-cache",
"Strict-Transport-Security": "max-age=31536000; includeSubDomains",
"x-ms-islandgateway": "_prdil102eusgb0_8",
"x-ms-igw-tracking-id": "[redacted]",
"mise-correlation-id": "[redacted]",
"x-ms-request-id": "[redacted]",
"x-ms-correlation-id": "[redacted]",
"X-Content-Type-Options": "nosniff",
"X-Frame-Options": "DENY",
"Server-Timing": "x-ms-igw-upstream-headers;dur=273.0,x-ms-igw-req-overhead;dur=2.0",
"x-ms-service-request-id": "[redacted]",
"x-ms-activity-vector": "00.00.IN.57.IN.2P.IN.06.00",
"x-ms-environment-id": "[redacted]",
"x-ms-tenant-id": "[redacted]",
"x-ms-subscription-id": "[redacted]",
"x-ms-dlp-re": "office365|False",
"x-ms-dlp-gu": "-|-",
"x-ms-dlp-ef": "-|-/-|-|-|-",
"x-ms-mip-sl": "-|-|-|-",
"x-ms-au-creator-id": "[redacted]",
"Timing-Allow-Origin": "*",
"x-ms-apihub-cached-response": "true",
"x-ms-apihub-obo": "false",
"x-ms-plex-failed": "false",
"Date": "Wed, 20 May 2026 16:40:44 GMT",
"Content-Length": "0",
"Expires": "-1"
}
}
