To configure your SMTP you would need to first check whether you are going to send using ISP or the server that hosts your domain. When you use your ISP as your SMTP server you need to make sure that authentcation is not enabled. If you are using Afrihost as your SMTP server than the server address would be smtp.afrihost.co.za.
When you use the incoming mail server to send out mails you would need to use the same address as the incoming mail server address and also you need to make sure authentication is enabled so that the server is able to. mail.domainname.tld.
SMTP Ports: 25/587