Cant send email (send message/smtp error)
I hope someone can help me with my problem.
So I created a droplet with 14.01 Ubuntu installed on it. I installed Virtualmin and created virtual instance for a domain. I need few users who will use only email. So from "edit users" in Virtualmin I created users and "emails only" set privilege. The users can go to https://domainname.com:20000 and check their mail in the webmin mail and can change the passwords there. Also from there sending mail is successful. But, from mail clients (Outlook and Postbox for example) after adding the account and fill with correct informations (mail, username, incoming and out coming mail) everything is ok and says it is connected to server. But when I try to send mail an error occurs. I attached an image with screenshots from Outlook and Postbox
I didn't touch nothing in Postfix server options or SMTP settings. Does someone can help me and tell me what should I do ?