Why are so many of my emails being rejected as Spam

Question

I've suddenly been unable to send emails both with and without attachments to many recipients. Various messages are coming back saying they've rejected it. It seems my email must be blocked or seemingly spam. I haven't changed anything, why is this suddenly happening. My usual IT guy can’t get to the bottom of it and said he has tried everything and I need to get in touch with the company that rejected it and ask them to whitelist me.  Well aside from this being many rejections, places like Hospitals are unlikely to do this.  He said it’s because companies have aggressive protection settings now but I can’t see that everyone would be having all their emails rejected? Can anyone help? Thank you.

Answer 1

Can you use the instruction here, change the email to plain text or rich text format (basically avoid the html format) and see if it goes through:

https://support.microsoft.com/office/change-the-message-format-to-html-rich-text-format-or-plain-text-in-outlook-338a389d-11da-47fe-b693-cf41f792fefa

Answer 2

There are several reasons why your emails might be getting rejected as spam. Here are some potential causes:

1. Spam Detection: Your messages may be detected as spam due to content or attachments that trigger spam filters. This can happen even if you haven't changed anything in your email practices.
2. Aggressive Security Settings: Many organizations, including hospitals, have implemented aggressive email filtering and security settings to protect against spam and phishing attacks. This can lead to legitimate emails being blocked.
3. IP Address Reputation: If your email server's IP address has been flagged for sending spam in the past, it may be blacklisted, causing your emails to be rejected.
4. Attachments and Content: Certain types of attachments or content within your emails may be flagged as suspicious. For example, if your attachments contain file types that are commonly associated with malware, they may be rejected.
5. Message Trace: To diagnose the issue, you can run a message trace to find out why your emails are being rejected. This can provide insights into whether your messages are being filtered, redirected, or experiencing delivery failures.

To resolve this issue, you may consider the following steps:

• Review the content and attachments of your emails to ensure they comply with common email standards.
• Contact the recipients' IT departments to inquire if your email address or domain can be whitelisted.
• Use the message trace feature to gather more information about the delivery status of your emails.

If the problem persists, you may want to consult with your IT support for further troubleshooting and potential solutions.

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References:

• Message Trace FAQ in Exchange Online
• External senders - Troubleshoot email sent to Microsoft 365