What is the address for POP3, IMAP, SMTP?

Question

postfix

Postfix + dovecot is configured on the server. When connecting mail clients, you must specify the addresses of the servers. Both smtp and imap(pop3) users connect to mydomain.com, but most email clients offer smtp.mydomain.com and pop(imap).mydomain.com by default. How can I make sure that users can connect with these default settings? Will it be correct to write an A record for smtp, pop and imap in the domain settings at the registrar, referring to mydomain.com. And will it be necessary for me in this case, when using SSL connections to send and receive mail by the client, to obtain a certificate for smtp.mydomain.com and pop(imap).mydomain.com?

Answer 1

Will it be correct to write an A record for smtp, pop and imap in the domain settings at the registrar, referring to mydomain.com.

yes, definitely
You can buy, you can self-signed. In any case, postfix+dovecot must be configured to work with the
P.S certificate.
ssl3 is leaky, so tls 1.2 is recommended