How to config Postfix to send external mail without use Relay of Google or other

I was able to configure Postfix to send external emails using Google's retransmission, but that's not what I want. I mean, I want to send mails through my own domain.

The Postfix was configured and it can receive email from externals domains.

However I'd like to send external mails without use Relay of Google or other one. How can I do it? What are the configs?

My internal email is: commercial@something.io

Versions: Ubuntu 17.10 (Artful Aardvark) ; Postfix 3.2.3

Below my setups;

The ports 25 and 587 are open in GCP where postfix was configured

There is an linux user commercial name created where postfix was configured

MX and A DNS were setup and below you can see report yielded from dig linux command:

Below my extra setups;

something.io.         59      IN      MX      10 mail.something.io.

mail.something.io.    59      IN      A       <SOMETHING IP ADDRESS>

$ dig MX something.io

; <<>> DiG 9.10.3-P4-Ubuntu <<>> MX something.io
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19811
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;something.io.                     IN      MX

;; ANSWER SECTION:
something.io.              39      IN      MX      10 mail.something.io.

;; Query time: 0 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Mon Nov 27 09:48:15 -02 2017
;; MSG SIZE  rcvd: 59

$ dig A mail.something.io

; <<>> DiG 9.10.3-P4-Ubuntu <<>> A mail.something.io
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 9197
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;mail.something.io.                        IN      A

;; ANSWER SECTION:
mail.something.io.         47      IN      A       35.188.104.163

;; Query time: 0 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Mon Nov 27 09:48:22 -02 2017
;; MSG SIZE  rcvd: 59

$ sudo postconf -n

alias_database = hash:/etc/aliases
alias_maps = hash:/etc/aliases
append_dot_mydomain = no
biff = no
compatibility_level = 2
home_mailbox = Maildir/
inet_interfaces = all
inet_protocols = all
mailbox_size_limit = 0
mydestination = $myhostname localhost.$mydomain localhost
myhostname = something.io
mynetworks = 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
myorigin = /etc/mailname
readme_directory = no
recipient_delimiter = +
relayhost =
smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
smtpd_tls_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
smtpd_use_tls = yes
virtual_alias_maps = hash:/etc/postfix/virtual

$ sudo postconf -M

smtp       inet  n       -       y       -       -       smtpd
submission inet  n       -       y       -       -       smtpd
pickup     unix  n       -       y       60      1       pickup
cleanup    unix  n       -       y       -       0       cleanup
qmgr       unix  n       -       n       300     1       qmgr
tlsmgr     unix  -       -       y       1000?   1       tlsmgr
rewrite    unix  -       -       y       -       -       trivial-rewrite
bounce     unix  -       -       y       -       0       bounce
defer      unix  -       -       y       -       0       bounce
trace      unix  -       -       y       -       0       bounce
verify     unix  -       -       y       -       1       verify
flush      unix  n       -       y       1000?   0       flush
proxymap   unix  -       -       n       -       -       proxymap
proxywrite unix  -       -       n       -       1       proxymap
smtp       unix  -       -       y       -       -       smtp
relay      unix  -       -       y       -       -       smtp
showq      unix  n       -       y       -       -       showq
error      unix  -       -       y       -       -       error
retry      unix  -       -       y       -       -       error
discard    unix  -       -       y       -       -       discard
local      unix  -       n       n       -       -       local
virtual    unix  -       n       n       -       -       virtual
lmtp       unix  -       -       y       -       -       lmtp
anvil      unix  -       -       y       -       1       anvil
scache     unix  -       -       y       -       1       scache
maildrop   unix  -       n       n       -       -       pipe flags=DRhu user=vmail argv=/usr/bin/maildrop -d ${recipient}
uucp       unix  -       n       n       -       -       pipe flags=Fqhu user=uucp argv=uux -r -n -z -a$sender - $nexthop!rmail ($recipient)
ifmail     unix  -       n       n       -       -       pipe flags=F user=ftn argv=/usr/lib/ifmail/ifmail -r $nexthop ($recipient)
bsmtp      unix  -       n       n       -       -       pipe flags=Fq. user=bsmtp argv=/usr/lib/bsmtp/bsmtp -t$nexthop -f$sender $recipient
scalemail-backend unix - n       n       -       2       pipe flags=R user=scalemail argv=/usr/lib/scalemail/bin/scalemail-store ${nexthop} ${user} ${extension}
mailman    unix  -       n       n       -       -       pipe flags=FR user=list argv=/usr/lib/mailman/bin/postfix-to-mailman.py ${nexthop} ${user}

Command to send an external mail:

echo "Body-Test" | mail -s "Subject-Test" externalname@outlook.com

$ mailq

8318C43C73      447 Sun Nov 26 16:29:01  commercial@something.c.intense-emblem-XXXXXX.internal
           (connect to mx2.hotmail.com[65.55.37.104]:25: Connection timed out)
                                         externalname@outlook.com

I'd like to send external mails without use Relay of Google or other one.
How can I do it? What are the configs?

Could you please check it and guide me to turn on the postfix to send externals mails through my own domain? Thanks