Some Internet Providers such as PLDT and Globe Telecoms blocks SMTP (out going mail server) port 25 other than their own servers. If you are unable to send email using mail.yourdomain.com or smtp.yourdomain.com using port 25 your can use the alternate settings.
I've used the following ports, however none is working.
For shared Linux cPanel and Windows hosting, use alternate SMTP port 26
For unlimited Windows hosting, use alternate SMTP port 2525
For unlimited Linux hosting, use alternate SMTP port 587
i'm a mobile user that connects in different network, what is your recommended solution for this.