You can run tor.exe without Tor browser in this way:
1) Copy torrc.defaults into the directory in which tor.exe is
2) Open cmd prompt windows
3) chdir to the directory where tor.exe is
4) Execute cmd line: tor.exe -f .\torrc.defaults
You will see tor is running and Socks listening on port 9150, Control listening on port 9151.
The keyserver TorBirdy is configured to use by default is a Tor Hidden Service, so yes. In the event you alter the default keyserver to a different one, the answer is also yes. Documentation for TorBirdy is here: https://trac.torproject.org/projects/tor/wiki/torbirdy
Note that by default, TorBirdy will configure your email account to use port 465 and not port 25 for the SMTP server. This in fact should be your default setting: you should not be using port 25 for your email over Tor as your username and password are sent in clear text and can be sniffed by the exit node.
Most providers use 465 for SSL/TLS and 587 for ...
Because of technical reasons (restricted by Thunderbird), it is not possible to apply the TorBirdy settings to specific email accounts.
Have a look at the Transparent Torification option, which allows you to keep all TorBirdy privacy settings intact except telling TorBirdy to use Tor (the proxy settings are cleared). This allows you to access a particular ...