Sorry to hear you're running into this problem. Hopefully, my response will be helpful.

Outbound emails from Outlook to Xeams (or any other email server) are sent via SMTP. Therefore, POP3 and IMAP are irrelevant. Try the following steps:

• Go to Server Configuration/SMTP Configuration
• Ensure the second port is listening on port 587. Leave the primary on 25.
• Configure your Outlook similar to the following image:
  
• This means Outlook will communicate on port 587 to send outbound emails. Initially, use "None" for Encryption method. Once you configure Xeams with SSL, you can switch that to STARTTLS.