Yes, but that's absolutely not recommended. Doing so would expose your passwords over a plain text connection for SMTP and IMAP authentication. This is an extremely bad idea (IMHO it borders on criminal negligence).
However, you are lucky as Let's Encrypt certificates are free to use and there is absolutely no reason not to use them. Furthermore, if you find a reason not to use them anyway, you could even use self-signed certificates, but you have to manually configure your clients to trust those. This might work for small environments and is what I did for my private stuff before Let's Encrypt was available.
Yes, but that's absolutely not recommended. Doing so would expose your passwords over a plain text connection for SMTP and IMAP authentication. This is an extremely bad idea (IMHO it borders on criminal negligence).
However, you are lucky as Let's Encrypt certificates are free to use and there is absolutely no reason not to use them. Furthermore, if you find a reason not to use them anyway, you could even use self-signed certificates, but you have to manually configure your clients to trust those. This might work for small environments and is what I did for my private stuff before Let's Encrypt was available.