my website need a sending mass mail.because my website is social network..but 000webhost is not support to mass mail.so,Can I change my email delivery server?
You can easily setup a script to use SMTP instead of the default php mailer of a web server.Depending if your site is online at the moment?
Be careful though. My site went down for a day for supposed "mass mailings".
If you want to send mass mail then the only way I see is that you have to upgrade your account.
or make the script use some SMTP server
You could use a PHP mail script to send mail through google gmail (the google apps engine is another similiar method) or you could just set up a yahoo group, which is really easy.