Windows 10 reached EOS (end of support) on October 14, 2025. If you are on Windows 10, see this article.

Avatar for Username

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More
Open

ProofPoint keeps blocking outgoing emails from Thunderbird, how can I resolve this?

Thunderbird Send and receive email
david replied
accounts66
accounts66

I keep getting emails like the one below. How can I stop Proofpoint from blocking emails like this? I can't get any response from Proofpoint.

Thank you.


Forwarded Message --------

Subject: Mail delivery failed: returning message to sender Date: Mon, 23 Mar 2026 15:32:49 -0400 From: Mail Delivery System <Mailer-Daemon@server240.web-hosting.com> To: [edited]@unexpectedwildliferefuge.org


This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:

[edited]@marshallsterling.com host mxb-00261401.gslb.pphosted.com [148.163.148.189] SMTP error from remote mail server after initial connection: 554 Blocked - see https://ipcheck.proofpoint.com/?ip=66.29.141.68

I keep getting emails like the one below. How can I stop Proofpoint from blocking emails like this? I can't get any response from Proofpoint. Thank you. -------- Forwarded Message -------- Subject: Mail delivery failed: returning message to sender Date: Mon, 23 Mar 2026 15:32:49 -0400 From: Mail Delivery System <Mailer-Daemon@server240.web-hosting.com> To: [edited]@unexpectedwildliferefuge.org This message was created automatically by mail delivery software. A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed: [edited]@marshallsterling.com host mxb-00261401.gslb.pphosted.com [148.163.148.189] SMTP error from remote mail server after initial connection: 554 Blocked - see https://ipcheck.proofpoint.com/?ip=66.29.141.68

Modified by christ1

All Replies (3)

david
david
  • Top 10 Contributor

Proofpoint is saying your IP is blocked. I encourage following their links to identify how to unblock this. or work with your email provider. Thunderbird sends mail from your IP address, but Thunderbird cannot change it.

accounts66
accounts66 Question owner

How do I follow Proofpoints links to identify how to unblock the email? Thunderbird is my email provider. Thank you.

david
david
  • Top 10 Contributor

NO. Thunderbird is only your email client, your assistant. Your email provider is the one who authorizes the account, the password, the storage for messages. This is often the name to the right of the @ sign in an email address, but not always. It is NEVER thunderbirdd.

Ask a question

You must log in to your account to reply to posts. Please start a new question, if you do not have an account yet.