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What would stop you being able to send emails via an Outlook /Hotmail account?

Making moves

I've recently experienced being unable to send emails via my hotmail / outlook email account to other addresses.

It all started after enabling 2-factor authentication on the account, then disabling it again. I had a suspected breech, due to a Microsoft community email problem....

Now, I can only post emails to other "hotmail" accounts, but to no others, except it I use the web interface.

Any ideas upon what's wrong, and how I can fix it ?





Making moves

I am unable to send messages with hotmail as well

Having the same issue with "Hotmail" - 



When I turned off the Anti-Virus application - AVAST, the message went through.... something to consider.


And ? your anti-virus program with this suggestion

Increase mailnews.tcptimeout from its default value of 60 seconds to 300 seconds using Tools -> Options -> Advanced -> General -> Connection timeout. This frequently solves the problem, especially when you have a wireless connection. This preference is only available in 1.5 or later. (In 3.x versions the setting is accessible only through the Config Editor - Tools->Options->Advanced->General->Config Editor.)

The default value is no longer 60, now the default value is 100
You can try 600 if you like

Config Editor
Search mailnews.tcptimeout
It is good practice to restart Thunderbird after editing preferences for your changes to take effect

It appears to be something to do with the way Avast's "Mail Shield" interacts with Thunderbird. 

As a test case, first without the "Mail Shield" installed, I sent a 1 liner plain text "test" message from one account to another, and it went through, no issues.

Then after installing "Mail Shield", I tried the same - this time, the mail message could not be sent, even after having edited the "tcptimeout" setting as described earlier. Again, the same error: timed out.

One thing I noticed, after installing "Mail Shield" my Thunderbird client went into a resync of all mail messages, however even after that had finished, I still could not send the simple plain text mail message (no attachments, simply one 1 word "test").

The problem only appears to be with sending from Microsoft mail accounts (I have several). If I switch the "From" account to a gmail or POP account then I have no issues.

Looking at the Thunderbird Troubleshooting report, the main difference between the Microsoft Accounts and the others, is that the Outgoing server uses a "Connection security" of "STARTTLS" whilst the others use " SSL/TLS".  Perhaps Avast's "Mail Shield" doesn't support STARTTLS ? Surely there must be others who have "Mail Shield" installed whilst using Thunderbird ?


Making moves

You might be unable to send emails from an Outlook/Hotmail account for several potential reasons. These could include issues like account suspension due to suspicious activity, technical glitches within the email system or on your device, entering incorrect login credentials, being blocked by other email service providers, hitting sending limits, having a blacklisted IP address, or using outdated software or settings. Checking for error messages, verifying account settings, and ensuring you're not exceeding sending limits are good initial steps to troubleshoot. If problems persist, contacting Microsoft support might be necessary for further assistance.