What should I do if I try to send an email because the server replies: "Can't open SMTP stream"?

How do I fix the problem?

What should I do if I try to send an email because the server replies: "Can't open SMTP stream"?
First you need to know if the smtp server requires authentication or not from the host/isp. If you are using email from a different provider than your isp, you probably need to use the ISPs outgoing mail server. ISPs do this for safety. Make sure you have smtp authentication enabled on your computer w/ the UN/PW entered correctly. Some ISPs are changing their SMTP port to 25, you could call them and ask so you can change the port in the program. If nothing works usually you can just remove the account from the client, restart the computer and add it again. You could also test telnetting the SMTP port. Open a dos/bash prompt and type in "telnet smtp.ispname.net 25" where you replace smtp.ispname.net with the actual smtp server name. You want to see the first thing it responds with is "220" and a server address. That means that you can contact the server. Type in "EHLO test.com". You want it to respond with the number 250 and usually they write something funny like "pleased to meet you". At this point, if you still can't connect to the smtp server via your client, disable your firewall and try again. If you still can't, contact your ISP.