CentOS 6.9
mail ver 2.6.6

I can't get a generic mapping to work correctly. Postfix seems to be appending the sender email address with this: (root). Please see attached screen shot.

It gets rejected by the server because it's deemed invalid/unsupported domain.

How do I get it to just use the email address alone. Why is it adding (root) to the end of the email address?

https://drive.google.com/file/d/1PW5...ew?usp=sharing

main.cf:
relayhost = [secure-email-813.luxsci.com]:587
smtp_use_tls = yes
smtp_sasl_auth_enable = yes
smtp_sasl_security_options =
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_tls_CAfile = /etc/ssl/certs/ca-bundle.crt
smtp_generic_maps = hash:/etc/postfix/generic

generic:
localhost email@domain.com
localhost6 email@domain.com
root email@domain.com
@SS-A.localdomain email@domain.com
localhost6.localdomain email@domain.com
@SS-A.localdomain.com email@domain.com
root@SS-A.localdomain email@domain.com
root@localhost6.localdomain6 email@domain.com

It's appending root because you are running "mail" command as root user. Therefore it will send an email as that user. That's completely fine.
As for mail getting rejected, do you have domain publicly registered ?
Is your domain allowed to relay mail through luxsci.com ? Possibly not as mail gets rejected by relay host, not google (since you emailed to gmail address).

Your screen shot is showing the contents of a log file. That doesn't really tell us what the email From actually said.
Can you show the headers of the email?

Please use [code] tags to paste code or output, for readability.

This sender email address does have the appropriate permissions to send from that relay server. It's working in another application on a windows server. Just postfix is having the problem.
Also, here's an image of an email sent from another server set up the same way but with different credentials. You can see that (root) was not appended to the sender address in the sixth line from the bottom. The from email address is in this format: <email.domain.com>. In the log of the problem server it is this: <email.domain.com (root)>

https://drive.google.com/file/d/1eU9...ew?usp=sharing

postqueue: warning: Mail system is down -- accessing queue directly
-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient-------
E3BB1BC42FC* 438 Tue Jun 18 21:38:00 root
to_address@gmail.com

-- 0 Kbytes in 1 Request.
[root@SS-A postfix]# postcat -vq E3BB1BC42FC*
postcat: dict_eval: const mail
postcat: dict_eval: const all
postcat: dict_eval: const
postcat: dict_eval: const
postcat: dict_eval: const
postcat: name_mask: all
postcat: dict_eval: const domain.com
postcat: dict_eval: const SS-A.domain.com
postcat: dict_eval: const domain.com
postcat: dict_eval: const Postfix
postcat: dict_eval: expand ${multi_instance_nameostfix}${multi_instance_name?$multi_instance_name} -> postfix
postcat: dict_eval: const postfix
postcat: dict_eval: const postdrop
postcat: dict_eval: expand $myhostname, localhost.$mydomain, localhost -> SS-A.domain.com, localhost.domain.com, localhost
postcat: dict_eval: const domain.com
postcat: dict_eval: const [secure-email-813.luxsci.com]:587
postcat: dict_eval: const /usr/libexec/postfix
postcat: dict_eval: const /var/lib/postfix
postcat: dict_eval: const /usr/sbin
postcat: dict_eval: const /var/spool/postfix
postcat: dict_eval: const pid
postcat: dict_eval: const localhost
postcat: dict_eval: const
postcat: dict_eval: const double-bounce
postcat: dict_eval: const nobody
postcat: dict_eval: const hash:/etc/aliases
postcat: dict_eval: const 20100319
postcat: dict_eval: const 2.6.6
postcat: dict_eval: const hash
postcat: dict_eval: const deferred, defer
postcat: dict_eval: const
postcat: dict_eval: expand $mydestination -> SS-A.domain.com, localhost.domain.com, localhost
postcat: dict_eval: expand $relay_domains -> SS-A.domain.com, localhost.domain.com, localhost
postcat: dict_eval: const TZ MAIL_CONFIG LANG
postcat: dict_eval: const MAIL_CONFIG MAIL_DEBUG MAIL_LOGTAG TZ XAUTHORITY DISPLAY LANG=C
postcat: dict_eval: const subnet
postcat: dict_eval: const
postcat: dict_eval: const +=
postcat: dict_eval: const -=+
postcat: dict_eval: const debug_peer_list,fast_flush_domains,mynetworks,permit_mx_backup_networks,qmqpd_authorized_clients,rel ay_domains,smtpd_access_maps
postcat: dict_eval: const
postcat: dict_eval: const bounce
postcat: dict_eval: const cleanup
postcat: dict_eval: const defer
postcat: dict_eval: const pickup
postcat: dict_eval: const qmgr
postcat: dict_eval: const rewrite
postcat: dict_eval: const showq
postcat: dict_eval: const error
postcat: dict_eval: const flush
postcat: dict_eval: const verify
postcat: dict_eval: const trace
postcat: dict_eval: const proxymap
postcat: dict_eval: const proxywrite
postcat: dict_eval: const
postcat: dict_eval: const
postcat: dict_eval: const 2
postcat: dict_eval: const 100s
postcat: dict_eval: const 100s
postcat: dict_eval: const 100s
postcat: dict_eval: const 100s
postcat: dict_eval: const 3600s
postcat: dict_eval: const 3600s
postcat: dict_eval: const 5s
postcat: dict_eval: const 5s
postcat: dict_eval: const 1000s
postcat: dict_eval: const 1000s
postcat: dict_eval: const 10s
postcat: dict_eval: const 10s
postcat: dict_eval: const 1s
postcat: dict_eval: const 1s
postcat: dict_eval: const 1s
postcat: dict_eval: const 1s
postcat: dict_eval: const 500s
postcat: dict_eval: const 500s
postcat: dict_eval: const 18000s
postcat: dict_eval: const 18000s
postcat: dict_eval: const 1s
postcat: dict_eval: const 1s
postcat: name_mask: subnet
postcat: inet_addr_local: configured 3 IPv4 addresses
postcat: inet_addr_local: configured 4 IPv6 addresses
postcat: been_here: 127.0.0.0/8: 0
postcat: been_here: [::1]/128: 0
postcat: mynetworks: 127.0.0.0/8 [::1]/128
postcat: dict_eval: const 127.0.0.0/8 [::1]/128
postcat: fatal: bad mail queue ID: E3BB1BC42FC*