To change your current IMAP mail server settings, open your email app and update the settings as follows:

• Incoming Mail Server (IMAP)
  • User Name: Enter your full email address
  • Password: Enter your email password
  • Server Name: imap.themessagingco.com.au
  • Port: 993
  • Security Type: SSL/TLS
  • Authentication: Password (Mail app) / Normal Password (Thunderbird) / Not applicable to Outlook
     
• Outgoing Mail Server (SMTP) 
  • User Name: Enter your full email address
  • Password: Enter your email password
  • Server Name: smtp.themessagingco.com.au
  • Port: 465 
  • Security Type: SSL/TLS
  • Authentication: Password (Mail app) / Normal Password (Thunderbird) / Not applicable to Outlook

If you require detailed steps, please refer to these guides: Modify mail server settings