Setting up email client but can't connect to SMTP server

I am a very new newbie in regards of setting email. I was following the instruction to set email client, the error message I get is "We couldn't connect to the outgoing(STMP) server. " I don't know from which part the problem starts, so I will try to list all the details here:

The email I want to setup is staff@mywebsite-alias.com, mywebsite-alias.com is an alias virtual server of mywebsite.com. Both websites are properly working. mywebsite-alias.com's DNS setting is as follow: MX RECORD: @ -> mail.mywebsite-alias.com A RECORD: mail.mywebsite-alias.com -> my virtual server's IP In virtualmin, under mywebsite-alias.com I did "Edit users -> Add a user to this server", and added “staff”, the "IMAP / POP3 / FTP login" being "staff.mywebsite-alias-com".

In Outlook, for account type I tried both IMAP and POP, "mail.mywebsite-alias.com:143" for Incoming Mail and "mail.mywebsite-alias.com:25" for Outgoing Mail, "Encryption Method" is "none" for both incoming and outgoing, but it keeps saying can't connect to SMTP.

So which setting should I look into to solve this problem?