Home Office PHP Web Server : MAIL

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Hi,

I'm reading the Ubuntu Server Guide and it talks about configuring 
Postfix and Dovecot.  It mentioned a spam module for Dovecot that 
appears to be an addon.

I'm thinking I only need/want SMTP port 25 and IMAPS on port 993.  I 
want the email messages to remain on the server.

Am I on the right track with Let's Encrypt, Postfix, and Dovecot, with 
the mail messages remaining on the server, and SMTP port 25 and IMAPS 
port 993?

Thank You for all your help!!
Keith