I understand that you are trying to to solve this, but you are posting to many things at once and lacking context. So,..
1) on screenshot using telnet you leak your public IPv6 so i can PRT this so I now know your FDQN you are trying to hide. If you want to anonymyze this you need anonymize this too,…
2) Your IP under this FDQN is (i will censor it to for your safety) 5.180.-4-.-1- I believe this IP is not part of cloudflare so you are not proxing, you just using cloudflare as NS (DNS) also visible on first screen from CF (DNS only not proxy), so cloudflare should not be an issue in this matter.
3) screen from MX is uncomplete and says nothing in this form.
4) screens from STMP connection if im not mistaken are not from your PHP server? Also irelevant
In sum I strongly believe that you are hiting filrewall close to your PHP server, you need look there. This mean write to your server provider, if it is behind NAT write to you ISP
edit: about HTTP port, if you are using smtp,imap and so these does not matter.