Bad outbound sender - repeat issue

Question

Hi we've recently been sending around 200 - 300 emails per day from our BD emails and this has not been an issue for months, however now when we attempt to do so we are hit with the "bad outbound sender" response and all of our mailings are spam blocked as the system believes the emails are compromised.

No matter how many times our email admin re-enables the account this continues to happen. We have done everything from warming up accounts slowly, to sending messages delayed and further fixes.

I am now at a stage where our primary source of lead generation is stunted, and it has been providing us nearly 10 appointments per week which has now been sat at an astonishing 0 for the last 4 weeks.

How can we solve this problem permanently?

Thanks,

Answer 1

Hello Lewis,

Good day!

Thanks for reaching out. I understand that you're experiencing a critical issue with your email sending capabilities, specifically:

• Your BD emails are being flagged as "bad outbound sender" and spam-blocked
• Despite re-enabling the account multiple times, the issue persists
• You've tried various fixes, including warming up accounts, delayed sending, and more
• This has severely impacted your lead generation, resulting in zero appointments for the past four weeks

To better understand and help resolve this issue, I have some questions:

1. Have you noticed any changes in your email content, templates, or sending patterns recently?
2. Are you using any third-party email services or tools that might be contributing to the issue?
3. Have you checked your email authentication settings (SPF, DKIM, DMARC)?
4. Are there any bounces, complaints, or abuse reports related to your email account?
5. Have you considered implementing email list cleaning or validation to ensure accurate recipient addresses?

The “bad outbound sender” response typically occurs when an email system detects unusual or suspicious activity from an account. This can be due to several reasons:

• Compromised Accounts: If any of your accounts are compromised, they might be flagged as a security risk.
• High Volume of Emails: Sending a large number of emails in a short period can trigger spam filters.
• Email Content: Certain patterns or keywords in your emails might be flagged as spam.
• Recipient Complaints: If recipients mark your emails as spam, it can affect your sender reputation.

Normally this is how to trouble shoot this situation:

Check for Compromised Accounts

• Review Account Activity: Check for any unusual sign-ins or actions.
• Reset Passwords: Reset passwords for any accounts that appear compromised.
• Enable Multi-Factor Authentication (MFA): This adds an extra layer of security.

Unblock Accounts

• Access Microsoft 365 Defender Portal:
  • Go to the Microsoft 365 Defender portal.
  • Sign in with your admin credentials.
• Navigate to Restricted Entities:
  • In the left-hand menu, select Email & Collaboration.
  • Click on Policies & Rules.
  • Select Threat policies.
  • Click on Tenant Allow/Block Lists
• Unblock the Account:
  • Find the account that is blocked.
  • Select the account and click Unblock.
  • Confirm the action. The restrictions should be removed within an hour.

Note*: Please understand that our initial reply may not always resolve the issue immediately. However, with your help and more detailed information, we can work together to find a solution.*

Given the complexity of this issue from your description I think the best thing to do is to investigate this issue in real time. It might be best to contact your IT administrator to create a support request - Get Support - Microsoft 365 Admin |Microsoft Learn so you can get real time assistance. Our technical experts have access to advanced tools and resources that allow them to thoroughly investigate issues, collect logs, and perform remote sessions to configure your settings. This approach will provide the most effective solution. Rest assured, I will keep an eye on the progress and follow up to ensure a permanent solution office.com after you open a service request.

Thank you for your patience and cooperation. I look forward to working to resolve your issue once your service request is opened. Have a great day.

Best regards,

Eleni | Microsoft Community Moderator.