Additional Information

-----Server Info------
Apache Version 2.4.46
PHP Version 5.4.45
MySQL Version 5.6.41-84.1
Architecture x86_64
Operating System linux
Shared IP Address 198.57.244.38
Path to Sendmail /usr/sbin/sendmail
Path to Perl /usr/bin/perl
Perl Version 5.10.1
Kernel Version 4.19.150-76.ELK.el6.x86_64

Before you ask, I have tried Sendmail, PHP and SMTP, though Sendmail is probably the right one for this server.