debian - Sendmail not sending mail as generic alias

Following the advice in this answer and the steps listed here, I've added the following to my /etc/mail/sendmail.mc file and compiled it with m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf. The end of.mc file itself:

dnl # Default Mailer setup
dnl # Masquerading options
FEATURE(`always_add_domain')dnl
MASQUERADE_AS(`debian')dnl
FEATURE(`allmasquerade')dnl

FEATURE(`masquerade_envelope')dnl
FEATURE(`genericstable',`hash -o /etc/mail/genericstable.db')dnl
GENERICS_DOMAIN_FILE(`/etc/mail/generics-domains')dnl
MAILER_DEFINITIONS
MAILER(`local')dnl
MAILER(`smtp')dnl

I created the /etc/mail/generics-domains file with:

mylinodeboxdomain.com
avirtualdomain.com

And created the /etc/mail/genericstable file with:

virtualuser    noreply@avirtualdomain.com

And restarted the sendmail service. Despite that, emails sent by virtualuser still seem to be coming from virtualuser@localhost rather than the desired noreply@avirtualdomain.com:

Received: from www.avirtualdomain.com (virtualuser@localhost)
    by mylinodeboxdomain.com (8.15.2/8.15.2/Submit) with SMTP id x6QIOIYY002415
    for ; Fri, 26 Jul 2019 14:24:18 -0400

I'm guessing my config is messed up, but as this is all new to me, I'm unsure what to change/remove.