Cyberpanel Email Issues..

I have a weird one in my opinion, I'm working on transferring a live email server over to a fresh new Linode since I was having issues with the previous one and also needed a slight downsize. It's all fine and working but my issue is that the mail server is only receiving mail on altmail.domain.com instead of the mail.domain.com that I would like just to standardize it.

The way that I had transferred everything over was just using a simple backup of the original server and moved it onto the new server for restoration. After that, I deleted all the subdomains that I did not want on this server because I want the new one to server email only and no websites. While I was setting it up, I made DNS records in CloudFlare for altmail.domain.com to allow myself to have two email servers temporarily while it was being setup, then I could test it by just changing the priorities of the 2 MX records.

But my issue now is that when I went to swap to mail.domain.com in DNS, I get SSL errors on my phone's email client and the Outlook desktop app. Below is the logs I saw in CyberPanel's email log

Aug 8 17:03:33 localhost dovecot: imap-login: Disconnected: Connection closed: SSL_accept() failed: error:0A000416:SSL routines::sslv3 alert certificate unknown: SSL alert number 46 (no auth attempts in 0 secs): user=<>, rip=[My Phone's IP], lip=[My Server's IP], TLS handshaking: SSL_accept() failed: error:0A000416:SSL routines::sslv3 alert certificate unknown: SSL alert number 46, session=<a5lav2wc5vpcvl0g>
Aug 8 17:03:45 localhost dovecot: imap(user@domain.com)<12200><cmhcvmwcb 9cvl0g="">: Disconnected: Logged out in=28 out=559 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0</cmhcvmwcb></a5lav2wc5vpcvl0g>

I've tried what I can think of but I'm not sure how I can get around this right now. Yes, I tried to reissue the mail server SSL certificate, but nothing, same issue.

Post Writing this: I'm noticing now that both altmail.domain.com and mail.domain.com, so both of them, are failing SSL when connecting via SMTP. I am still able to successfully send and recieve emails via snappymail in a browser, but this is not my preferred method.

Any help would be appreciated.

Edit: I found that the issue is involved with the server failing to obtain an SSL cert from Let's Encrypt. Can't figure out why.

[08.08.2023_17-36-56] Status Code: 200 for: http://www.domain.com/.well-known/acme-challenge/domain.com
[08.08.2023_17-37-06] Status Code: 200 for: http://domain.com/.well-known/acme-challenge/domain.com
[08.08.2023_17-37-08] /root/.acme.sh/acme.sh --issue -d domain.com -d www.domain.com --cert-file /etc/letsencrypt/live/ajp.network/cert.pem --key-file /etc/letsencrypt/live/domain.com/privkey.pem --fullchain-file /etc/letsencrypt/live/domain.com/fullchain.pem -w /usr/local/lsws/Example/html -k ec-256 --force --server letsencrypt
[08.08.2023_17-37-09] Failed to obtain SSL for: domain.com and: www.domain.com
[08.08.2023_17-37-09] Trying to obtain SSL for: domain.com
[08.08.2023_17-37-09] /root/.acme.sh/acme.sh --issue -d ajp.network --cert-file /etc/letsencrypt/live/domain.com/cert.pem --key-file /etc/letsencrypt/live/domain.com/privkey.pem --fullchain-file /etc/letsencrypt/live/ajp.network/fullchain.pem -w /usr/local/lsws/Example/html -k ec-256 --force --server letsencrypt
[08.08.2023_17-37-10] Failed to obtain SSL, issuing self-signed SSL for: domain.com
[08.08.2023_17-37-10] {'email@domain.com': (550, b'5.1.1 email@domain.com: Recipient address rejected: User unknown in virtual mailbox table')}
[08.08.2023_17-37-11] Self signed SSL issued for domain.com.