You can use the hook feature to automatically send mail when a commit occurs. Add the following to .hg/hgrc:

[hooks]
commit = commithook

And put this in a file called commithook in your path:

SUBJECT=`hg log -r $NODE | grep "^summary:" | cut -b 14-`
hg log -vpr $NODE | mail -s "commit: $SUBJECT" commit-list@example.com

And something like this can be used for closing bugs in roundup:

ISSUE=`hg log -vr $NODE | grep -o "\<fix:[[:alnum:]]*" | head -n 1 | sed s/fix://`
[ -z $ISSUE ] && exit
SUBJECT=`hg log -r $NODE | grep "^summary:" | cut -b 14-`
hg log -vr $NODE | mail -s "[$ISSUE] [status=testing] commit: $SUBJECT" roundup@example.com