SMTP is commonly used in client mails like Outlook.
It uses port 25 but you can try also port 26 in case your ISP blocks the port 25.
Some ISP force users to configure SMTP to pass thru their network so that all mails can be monitored. PLDT Smart Bro has recently moved to this scheme. If you are a Smart Bro user, you now must replace your SMTP to: smtpdsl4.pldtdsl.net
You must also check in the mail setup: "My server requires autehntication". If you do not check it, mails will not be sent out.
