Done that, still the same issue.
hostname -f
alpha.xxxx.co.uk
hostname -s
aplha
/var/log/maillog
Mar 7 12:08:42 alpha logger: sendmail: CALLER="php-fpm: pool default" PWD="/home/kloxo/httpd/webmail/roundcube" BAN="no"
Mar 7 12:08:42 alpha send: new msg 45090226
Mar 7 12:08:42 alpha send: info msg 45090226: bytes 440 from <contact@xxxx.co.uk> qp 2481 uid 48
Mar 7 12:08:42 alpha send: starting delivery 7: msg 45090226 to remote XXXXXX@gmail.com
Mar 7 12:08:42 alpha send: status: local 0/10 remote 1/60
Mar 7 12:08:42 alpha imap4: tcpserver: status: 1/40
Mar 7 12:08:42 alpha imap4: tcpserver: pid 2483 from ::1
Mar 7 12:08:42 alpha imap4: tcpserver: ok 2483 alpha.xxxx.co.uk:::1:143 :::1::55926
Mar 7 12:08:42 alpha imap4: DEBUG: Connection, ip=[::1]
Mar 7 12:08:42 alpha imap4: INFO: LOGIN, user=contact@xxxx.co.uk, ip=[::1], protocol=IMAP
Mar 7 12:08:42 alpha imap4: INFO: LOGOUT, user=contact@xxxx.co.uk, ip=[::1], headers=0, body=0, rcvd=490, sent=274, time=0
Mar 7 12:08:42 alpha imap4: tcpserver: end 2483 status 0
Mar 7 12:08:42 alpha imap4: tcpserver: status: 0/40
Mar 7 12:08:42 alpha send: delivery 7: deferral: Sorry,_I_wasn't_able_to_establish_an_SMTP_connection._(#4.4.1)/
Mar 7 12:08:42 alpha send: status: local 0/10 remote 0/60