https://shop.mydomain.com/help/article/email-client-setup-mozilla-thunderbird

Select Edit --> Account Settings

For the rick@crowhurst.net Entry:

SERVER SETTINGS
     Server Type:            IMAP Mail Server
     Server Name:            imap.crowhurst.net
     User Name:              rick@crowhurst.net
     Port:                   143
     Connection Security:    None
     Authentication method:  Password, transmitted insecurely


At the bottom of the list in the left-hand panel -- Select Outgoing Server (SMTP) 

You'll need an entry for smtp.crowhurst.net, and it should be set as the default

     Description:            crowhurst.net mail server
     Server Name:            smtp.crowhurst.net
     Port:                   587
     User Name:              rick@crowhurst.net
     Authentication method:  Normal password
     Connection Security:    STARTTLS

     Password:               Blitzen3135