How to get sendmail to send mail?

I’ve been happily beavering away on a Centos 7 droplet. I set up a LAMP stack and got few websites running in virtual hosts. I’ve now run into an annoying issue: the php mail() function isn’t working.

As a test I installed Drupal 7 on one of the sites. At first the form was submitted instantly but nothing was sent. After installing sendmail the form hangs for a while and I’m getting this in /var/log/maillog:

Jul 16 22:58:29 myhostname sendmail[18792]: My unqualified host name (myhostname) unknown; sleeping for retry
Jul 16 22:59:29 myhostname sendmail[18792]: unable to qualify my own domain name (myhostname) -- using short name
Jul 16 22:59:29 myhostname sendmail[18792]: alias database /etc/aliases rebuilt by myusername
Jul 16 22:59:29 myhostname sendmail[18792]: /etc/aliases: 76 aliases, longest 10 bytes, 771 bytes total
Jul 16 23:02:21 myhostname sendmail[18838]: My unqualified host name (myhostname) unknown; sleeping for retry
Jul 16 23:03:21 myhostname sendmail[18838]: unable to qualify my own domain name (myhostname) -- using short name
Jul 16 23:03:23 myhostname sendmail[18838]: My unqualified host name (myhostname) unknown; sleeping for retry
Jul 16 23:04:23 myhostname sendmail[18838]: unable to qualify my own domain name (myhostname) -- using short name
Jul 16 23:04:23 myhostname sendmail[18838]: w6GM3LxY018838: Authentication-Warning: myhostname: apache set sender to recipient@example.com using -f
Jul 16 23:04:23 myhostname sendmail[18838]: w6GM3LxY018838: from=recipient@example.com, size=429, class=0, nrcpts=1, msgid=<201807162203.w6GM3LxY018838@myhostname>, relay=apache@localhost
Jul 16 23:04:23 myhostname sendmail[18838]: w6GM3LxY018838: to=recipient@example.com, ctladdr=recipient@example.com (48/48), delay=00:01:02, xdelay=00:00:00, mailer=relay, pri=30429, relay=[127.0.0.1] [127.0.0.1], dsn=4.0.0, stat=Deferred: Connection refused by [127.0.0.1]

I then added this to the /etc/httpd/sites-available/example.com.conf file:

<Directory /var/www/example.com/public_html>
	php_admin_value sendmail_path "/usr/sbin/sendmail -t -i -fwebsite@example.com"
</Directory>

That results in:

Jul 17 12:06:48 myhostname sendmail[20949]: My unqualified host name (myhostname) unknown; sleeping for retry
Jul 17 12:07:48 myhostname sendmail[20949]: unable to qualify my own domain name (myhostname) -- using short name
Jul 17 12:07:48 myhostname sendmail[20949]: My unqualified host name (myhostname) unknown; sleeping for retry
Jul 17 12:08:48 myhostname sendmail[20949]: unable to qualify my own domain name (myhostname) -- using short name
Jul 17 12:08:48 myhostname sendmail[20949]: w6HB7mFh020949: Authentication-Warning: myhostname: apache set sender to website@example.com using -f
Jul 17 12:08:50 myhostname sendmail[20949]: w6HB7mFh020949: from=website@example.com, size=476, class=0, nrcpts=1, msgid=<201807171107.w6HB7mFh020949@myhostname>, relay=apache@localhost
Jul 17 12:08:50 myhostname sendmail[20949]: w6HB7mFh020949: to=myvps@email.com, ctladdr=website@example.com (48/48), delay=00:01:02, xdelay=00:00:00, mailer=relay, pri=30476, relay=[127.0.0.1] [127.0.0.1], dsn=4.0.0, stat=Deferred: Connection refused by [127.0.0.1]

I suspect the issue is my /etc/hosts and/or /etc/mail/local-host-names file but I’m at a loss at this stage.

# cat /etc/hosts
# The following lines are desirable for IPv4 capable hosts
127.0.0.1 myhostname myhostname
127.0.0.1 localhost.localdomain localhost
127.0.0.1 localhost4.localdomain4 localhost4

# The following lines are desirable for IPv6 capable hosts
::1 myhostname myhostname
::1 localhost.localdomain localhost
::1 localhost6.localdomain6 localhost6

# cat /etc/mail/local-host-names
# local-host-names - include all aliases for your machine here.

Any guidance gratefully received!