The recommended way to install the buildbot is to create a dedicated account for the buildmaster. If you do this, the account will probably have a distinct email address (perhaps buildmaster@example.org). Then just arrange for this account's email to be delivered to a suitable maildir (described in the next section).
If the buildbot does not have its own account, “extension addresses”
can be used to distinguish between email intended for the buildmaster
and email intended for the rest of the account. In most modern MTAs,
the e.g. foo@example.org account has control over every email
address at example.org which begins with "foo", such that email
addressed to account-foo@example.org can be delivered to a
different destination than account-bar@example.org. qmail
does this by using separate .qmail files for the two destinations
(.qmail-foo and .qmail-bar, with .qmail
controlling the base address and .qmail-default controlling all
other extensions). Other MTAs have similar mechanisms.
Thus you can assign an extension address like foo-buildmaster@example.org to the buildmaster, and retain foo@example.org for your own use.