Trying to set up Catch-All Email Address with Sendmail - email

Question

I'm trying to create a catchall email address with Sendmail (it will be used to catch email bounces for Oceth's OEMPro).
First I started by creating a new user:
# useradd -s /bin/false bounces
# passwd bounces
Then I created & opened a virtusertable file with vim virtusertable and added:
bounces#sub.example.com bounces
#sub.example.com bounces#sub.example.com
Then I added the below line to sendmail.mc near the end but before the MAILER_DEFINITIONS of with
FEATURE(`virtusertable', `hash -o /etc/mail/virtusertable.db')dnl
Finally, I ran
# make
Updating databases ...
Reading configuration from /etc/mail/sendmail.conf.
Validating configuration.
Creating /etc/mail/databases...
Updating auth ...
sasl2-bin not installed, not configuring sendmail support.
To enable sendmail SASL2 support at a later date, invoke "/usr/share/sendmail/update_auth"
Creating /etc/mail/relay-domains
# Optional file...
Updating Makefile ...
Reading configuration from /etc/mail/sendmail.conf.
Validating configuration.
Creating /etc/mail/Makefile...
Updating sendmail.cf ...
The following file(s) have changed:
/etc/mail/sendmail.cf
** ** You should issue `/etc/init.d/sendmail reload` ** **
# service sendmail reload
* Reloading Mail Transport Agent (MTA) sendmail [ OK ]
# service sendmail restart
* Restarting Mail Transport Agent (MTA) sendmail [ OK ]
After all this it does not seem to be working, how can I test this properly. I've tried sending an email to bounces#sub.example.com but when I look in /var/mail/ I don't see the bounces user.
# ls /var/mail/
root www-data other-user
I created a MX DNS record for this too, e.g. sub.example.com.
The other indication it is not working correctly is that we are getting a 504 error when we try to use this email address as our POP3 Monitoring method in Oceth's OEMPro.
UPDATE
I tried running the below commands as root, in an attempt to debug the issue but I'm not clear what it's telling me.
root:/# sendmail -d60.5 -bv no-such-user#sub.example.com
map_lookup(dequote, other-user, %0=other-user) => NOT FOUND (0)
map_lookup(host, sub.example.com, %0=sub.example.com) => sub.example.com. (0)
no-such-user#sub.example.com... deliverable: mailer esmtp, host sub.example.com., user no-such-user#sub.example.com
root:/# sendmail -d60.5 -bv bounces#sub.example.com
map_lookup(dequote, other-user, %0=other-user) => NOT FOUND (0)
map_lookup(host, sub.example.com, %0=sub.example.com) => sub.example.com. (0)
bounces#sub.example.com... deliverable: mailer esmtp, host sub.example.com., user bounces#sub.example.com
I'm not sure why it first tries to look up another user on our system called other-user
UPDATE 2
After running # echo '$=w' | sendmail -bt I get the following result.
# echo '$=w' | sendmail -bt
ADDRESS TEST MODE (ruleset 3 NOT automatically invoked)
Enter <ruleset> <address>
> localhost
ip-1??-??-??-??5
[1??.??.??.??5]
ip-1??-??-??-??5.ec2.internal
[127.0.0.1]
ip-172-31-31-167.eu-west-1.compute.internal
In sendmail.mc I've changed FEATURE(virtusertable', hash -o /etc/mail/virtusertable.db')dnl to FEATURE(virtusertable', hash -o /etc/mail/virtusertable.db')dnl, basically I just removed the -o flag.
Then I updated /etc/mail/local-host-names to include sub.example.com, so now it reads:
localhost
ip-17?-??-??-?67.eu-west-1.compute.internal
sub.example.com
Then I ran:
# service sendmail restart
* Restarting Mail Transport Agent (MTA) sendmail
# echo '$=w' | sendmail -bt
ADDRESS TEST MODE (ruleset 3 NOT automatically invoked)
Enter <ruleset> <address>
> localhost
ip-1??-??-??-??5
[1??.??.??.??5]
ip-1??-??-??-??5.ec2.internal
[127.0.0.1]
sub.example.com
ip-17?-??-??-?67.eu-west-1.compute.internal
After sending an email to bunces#sub.example.com I still don't see the mailbox in /var/mail/
# ls /var/mail/
root www-data other-user
I also still get the 504 error in the OEMPro app when I try to configure it with these settings.

Answer 1

Sendmail consults virtusertable only for deliveries to local email domains (listed in $=w) and virtual domains (listed in $={VirtHost}). It seems that sub.example.com is not listed in any of them.
You can add sub.example.com to list of local email domains by listing it in file /etc/mail/local-host-names (one domain/name per line). After modifying the file restart sendmail daemon or send HUP signal to sendmail daemon.
You can check content of $=w by executing the following command as root:
echo '$=w' | sendmail -bt
Sendmail by default automagically adds some "guesswork" to $=w.
Extra hint:
Do not use -o (optional) flag in FEATURE(virtusertable). Without the flag sendmail refuses to start when compiled version of virtusertable is unawailable.