Hello,
My i-MSCP is 1.3.0.I found send mail to gmail it's will undelivered.
It's error message is
Quote
The IP you're using to send mail is not authorized to 550-5.7.1 send email directly to our servers. Please use the SMTP relay at your 550-5.7.1 service provider instead. Learn more at 550 5.7.1 https://support.google.com/mail/answer/10336 f74si9445325iod.184 - gsmtp (in reply to end of DATA command)
But I search google and edit main.cf.I edit mydestination
Quotemydestination = $myhostname, $mydomain
to
Quotemydestination = localhost, $myhostname, $mydomain
And restart postfix.It's can send mail to gmail.Please fix it.