Installation of QMT with the many-domain option, to which QMT will eventually 
fully migrate, utilizes the dovecot communities' RPMS and authenticates by sql 
query not the vpopmail driver, so, maintenance of a dovecot .qt RPM is no longer 
necessary, and will most likely lead to more timely updates.

IMAP Many-Domain alias domain authentication solution:

As a temporary fix for alias domains until something seamless and permanent is in place for dovecot IMAP/POP3 do the following:

# echo "create table aliasdomains (domain char(96) not null ,alias char(96) not null)" | mysql -u root -p vpopmail
# echo "insert into aliasdomains  (domain, alias) values ('realdomain.tld', 'aliasdomain.tld')" | mysql -u root -p vpopmail

Change password query in 'dovecot-sql.conf.ext'

# passdb query to retrieve the password. It can return fields:
password_query = SELECT CONCAT( pw_name ,'@', pw_domain ) AS user, \
  pw_passwd AS password, \
  pw_dir as userdb_home, \
  89 AS userdb_uid, \
  89 AS userdb_gid \
  FROM vpopmail vp \
  LEFT JOIN aliasdomains ad ON ad.alias = '%d' \
  WHERE  ( vp.pw_domain = ad.domain  OR vp.pw_domain = '%d') AND ( vp.pw_name = '%n' )

# doveadm auth test user@aliasdomain.tld xxx
passdb: user@aliasdomain.tld auth succeeded
extra fields:
  user=user@realdomain.tld

  original_user=user@aliasdomain.tld

# doveadm auth test user@realdomain.tld xxx
passdb: user@realdomain.tld auth succeeded
extra fields:
  user=user@realdomain.tld

For the future I'll look into submission and smtps authentication.