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Cannot send emails: Error "Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) smtp.office365.com was lost in the middle of the transaction. Try again"

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  • Last reply by sfhowes

Cardinal Fang
Cardinal Fang
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I keep getting this error message when trying to send emails through my Hotmail in Thunderbird: "Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) smtp.office365.com was lost in the middle of the transaction. Try again."

I tried the steps online in the support article at https://support.mozilla.org/en-US/kb/cannot-send-messages. I have tried deleting all the saved passwords as other answers to this problem have suggested. Nothing has worked. I have double checked the SMTP setting and they are correct.

If I turn off my VPN I can send messages. However as my wifi connection is shared and not secure, this isn't an ideal solution.

I'm sending a screenshot of my server settings. Email provider: Microsoft Outlook (formerly Hotmail) Firewall & antivirus: Bitdefender Total Security VPN: Bitdefender VPN Operating System: Windows 8.1 Thunderbird Version: 68.9.0 (32-bit)

I keep getting this error message when trying to send emails through my Hotmail in Thunderbird: "Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) smtp.office365.com was lost in the middle of the transaction. Try again." I tried the steps online in the support article at https://support.mozilla.org/en-US/kb/cannot-send-messages. I have tried deleting all the saved passwords as other answers to this problem have suggested. Nothing has worked. I have double checked the SMTP setting and they are correct. If I turn off my VPN I can send messages. However as my wifi connection is shared and not secure, this isn't an ideal solution. I'm sending a screenshot of my server settings. Email provider: Microsoft Outlook (formerly Hotmail) Firewall & antivirus: Bitdefender Total Security VPN: Bitdefender VPN Operating System: Windows 8.1 Thunderbird Version: 68.9.0 (32-bit)
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sfhowes
sfhowes
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Your settings are correct, and sending works without the VPN, so I think you have to consult Bitdefender support to figure out how to send through their VPN - with any mail client. BD, even without the VPN, is a known source of issues with TB, unless the TB exe and profile folder are excluded from all BD mail and secure-connection scanning.