Is your CSF firewall allowing all common mail ports (25, 465, 587, 110, 143, 995, 993)? Check incoming & outgoing. I can manually connect to that Gmail SMTP address via telnet:
% telnet 142.251.9.26 25
Trying 142.251.9.26...
Connected to rc-in-f26.1e100.net.
Escape character is '^]'.
220 mx.google.com ESMTP d8-20020a170906174800b00a2d4e52c6f2si5357323eje.126 - gsmtp