mydestination = example.com, test.com

# systemctl reload postfix     <- CentOS7, 8

example.com and test.com are the same

ex.
user01@example.com = user01@test.com

virtual_alias_domains = test.com
virtual_alias_maps = hash:/etc/postfix/virtual

# systemctl reload postfix     <- CentOS7, 8

test.com        anything
user1@test.com  user1
user2@test.com  user2

# useradd user1
# useradd user2
# postmap /etc/postfix/virtual

virtual_mailbox_domains = test1.com  test2.com
virtual_mailbox_maps = hash:/etc/postfix/virtual-mailbox
virtual_uid_maps = static:2000
virtual_gid_maps = static:2000
virtual_mailbox_base = /var/spool/virtual

# groupadd -g 2000 vmail
# groupadd -u 2000 -g vmail vmail

# mkdir /var/spool/virtual
# chown -R 2000,2000 /var/spool/virtual

# systemctl reload postfix     <- CentOS7, 8

user1@test1.com          test1.com/user1/Maildir/
user2@test1.com          test1.com/user2/Maildir/
user10@test2.com         test2.com/user10/Maildir/
user11@test2.com         test2.com/user11/Maildir/

# postmap /etc/postfix/virtual-mailbox