Laravel send email connection could not be established [connection timeout #110]

I have a send email feature on my project. I'm using Laravel's mailer (SwiftMailer) to do this. The error is that, on some network, the email was successfully sent, but on other network, it will display the error:

Connection could not be established with host smtp.gmail.com [connection time out #110]

Can anybody help to find the issues ?

via Chebli Mohamed