Letsencrypt certificate for mail server

Server
1

How can i create Letsencrypt certificate for smtp/imap mail server?
when i tried the below command, faced error

[root@server1 letsencrypt]# certbot certonly -d mail.server.co.uk |
Saving debug log to /var/log/letsencrypt/letsencrypt.log |
|
How would you like to authenticate with the ACME CA? |

                                                                                • |
                                                                                  1: Apache Web Server plugin - Beta (apache) |
                                                                                  2: Spin up a temporary webserver (standalone) |
                                                                                  3: Place files in webroot directory (webroot) |
                                                                                • |
                                                                                  Select the appropriate number [1-3] then [enter] (press ‘c’ to cancel): 2 |
                                                                                  Plugins selected: Authenticator standalone, Installer None |
                                                                                  Starting new HTTPS connection (1): acme-v02.api.letsencrypt.org |
                                                                                  Obtaining a new certificate |
                                                                                  Performing the following challenges: |
                                                                                  http-01 challenge for mail.ibiidi.co.uk |
                                                                                  Cleaning up challenges |
                                                                                  Problem binding to port 80: Could not bind to IPv4 or IPv6. |
                                                                                  [root@server1 letsencrypt]#
2

Hello. If it's okay, I'm going to close this topic, so the conversation can continue in the other one without getting confused.