Simple virtual user setup with multiple domains

[Unicorn]

Hello everyone,

I apologize in advance if these seem like a trivial question, I am
quite new to this and the amount of config files and options is a
little overwhelming. :)

I am currently running three mailservers that each serve one domain
with real user accounts, which is quite a pain to manage. I would like
to instead have one server be the MX for all of my domains, with
virtual users and their maildirs in a strucure like
/home/vmail/domain/user/Maildir.

In the process of writing my email I have written all my
configurations to the best of my ability, but I would appreciate your
feedback on any errors or suggestions for improvements, especially
since I intend to eventually make this into a guide:


######## /etc/mail/smtpd.conf #######################################
pki mx.maildomain.tld cert "/etc/ssl/mx.maildomain.tld.fullchain.pem"
pki mx.maildomain.tld key "/etc/ssl/private/mx.maildomain.tld.key"

# Junk filters, rspamd also for DKIM signing
filter check_dyndns phase connect match rdns regex { '.*\.dyn\..*',
'.*\.dsl\..*' } junk
filter check_rdns phase connect match !rdns junk
filter check_fcrdns phase connect match !fcrdns junk
filter rspamd proc-exec "filter-rspamd"

# Tables
table aliases file:/etc/mail/custom_aliases
table accounts file:/etc/mail/accounts
table domains {firstdomain.tld, seconddomain.tld, maildomain.tld}

# Listen for incoming mail and send through filters
listen on all tls pki mail.regrow.earth filter { check_dyndns,
check_rdns, check_fcrdns, rspamd }

# Listen for, authenticate and DKIM-sign outgoing mail requests
listen on all port submission tls-require pki mx.maildomain.tld auth
<accounts> filter rspamd

action "deliver_local" maildir
/home/vmail/{%dest.domain}/{%dest.user}/Maildir junk alias <aliases>
user vmail
action "outbound" relay helo mx.maildomain.tld

# Match incoming mail
match from any for domain <domains> action "deliver_local"
match for local action "deliver_local"

# Match outgoing mail
match from any auth for any action "outbound"
match for any action "outbound"
#####################################################################


######## /etc/dovecot/conf.d/10-auth.conf ###########################
passdb {
  driver = passwd-file
  args = scheme=BLF-CRYPT /etc/mail/accounts
}
userdb {
  driver = static
  args = uid=vmail gid=vmail home=/home/vmail/%d/%u
}
#####################################################################


######## /etc/mail/accounts #########################################
ad...@fistdomain.tld:passwordhashfromsmtpctl
ad...@seconddomain.tld:passwordhashfromsmtpctl
unic...@seconddomain.tld:passwordhashfromsmtpctl
#####################################################################

Is it possible to combine virtual users with an alias table as I have
in action "deliver_local"?

Example entry in alias table:
cont...@firstdomain.tld: admin+cont...@firstdomain.tld

Will this deliver to the folder "contact" of ad...@firstdomain.tld?
In 'action "deliver_local"', is it correct to use {%dest.user} for
this purpose?


Also, how does dkim signing with rspamd work for multiple domains?
Right now my /etc/rspamd/local.d/dkim-signing.conf looks like this:

##############################################################
allow_username_mismatch = true;

domain {
    firstdomain.tld {
        path = "/etc/mail/dkim/firstdomain.tld.key";
        selector = "blah";
    }
}
##############################################################

Will it work automatically by simply entering eg. 'seconddomain.tld
{...}' with its respective keyfile and selector?


Thanks a lot in advance, I appreciate any answers, even if incomplete!
:)

Best,
Unicorn