Later thought …
it is quite clever for this spambot to hide behind svchost.exe since this process requires outbound permission in those firewalls that have outbound controls.
However, if you have a firewall on your system with outbound control and since you do not use an email client you can use avast’s Internet Mail provider to your advantage to stop this spambot dead in its tracks while you hunt it down.
If you have such a firewall then remove outbound permission to ashMaiSv.exe and deny any future requests for outbound access for it. This will not stop the spambot from running on your system but it will prevent it from sending out the spam from your system and allow you time to find and eliminate it.