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

**Intermittent error when forwarding emails with attachments (IMAP, Windows 11)**

Thunderbird Attachments
Tiitus Halonen
Tiitus Halonen

Hello,

I'm experiencing an intermittent issue when forwarding emails with attachments (large and small) in Thunderbird on Windows 11. The error message reads:

  • "Sending the message failed. An error occurred while attaching [filename]. Check that you have the right permissions to read the file."*

The issue is not consistent — the same message can often be forwarded successfully later (as in the next day).

    • Environment:**

- Thunderbird (latest version) - Windows 11 - IMAP account - Windows Defender active

    • What I have tried:**
    • Suspected root causes:**

- Windows Defender or other AV software briefly locking the temporary file while Thunderbird tries to read it during forwarding.

Has anyone else encountered this, and is there a more permanent fix? Is there a known bug related to this behavior?

Thank you.

Hello, I'm experiencing an intermittent issue when forwarding emails with attachments (large and small) in Thunderbird on Windows 11. The error message reads: *"Sending the message failed. An error occurred while attaching [filename]. Check that you have the right permissions to read the file."* The issue is not consistent — the same message can often be forwarded successfully later (as in the next day). **Environment:** - Thunderbird (latest version) - Windows 11 - IMAP account - Windows Defender active **What I have tried:** **Suspected root causes:** - Windows Defender or other AV software briefly locking the temporary file while Thunderbird tries to read it during forwarding. Has anyone else encountered this, and is there a more permanent fix? Is there a known bug related to this behavior? Thank you.

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