When I use a Profile Password in Thunderbird 52.1.1 32-bit for Windows 10 Pro v1607, the latest update that I just installed today (May 18, 2017) prevents me from sending any outgoing mail. Here are the steps to reproduce: 1) Open Thunderbird and go to the Tools menu, select Profile Password, and then Password Manager. 2) Click on the "Set/Change Password" button and enter your desired password and click "OK." 3) Quit Thunderbird, then re-launch Thunderbird. 4) Before Thunderbird displays any e-mail, you're prompted to enter your new Profile Password. Do so and click OK. 5) Click on the "Write" icon to start a new message. On my computer, this strangely brings up the Profile Password prompt again. 6) Enter your Profile Password and click OK. 7) Write your message and then click on the "Send" icon. On my computer, nothing happens. 8) When you're ready to give up, click on the window's X to close it. You should then see a prompt stating, "Thunderbird is currently in the process of sending a message. Would you like to wait until the message has been sent before quitting or quit now?" with the options to either "Wait" or "Quit." If you click "Wait," nothing ever happens. You'll wait forever. Because of this, there is no way to send e-mail from Thunderbird if you use a Profile Password. Note that until the most recent update, steps 1-8 were still valid. However, as a ninth step, if after closing the e-mail that refused to send you then tried to send another e-mail, that one would work. But with the most recent 5/18/2017 update, this workaround no longer allows the second e-mail to send. Thank you!