Possibly missing some TXT/CNAME records (for SPF, DKIM, DMARC if so?)
You are using a hostname like yourdomain.com which is (proxied) rather than the unproxied (DNS-only) like mail.yourdomain.com (possible this one not existing or is instead of being ) at the DNS tab of Cloudflare dashboard, in your e-mail client for sending/receiving server (MS Outlook, Mozilla Thunderbird, etc.)
May I suggest checking below article if your e-mail records (usually the A mail and the MX record) are configured properly while you are using Cloudflare for your domain name:
Nevertheless, using online tools on the links below you could test and troubleshoot more what is going on with your e-mails:
Otherwise, you might have to troubleshoot if the port like 110/143/993/995 and 25/465/587 is open at your hosting provider and contact hosting provider to check this for you. If they are not open, then I am afraid you may not be able to receive any emails from using that web hosting/email provider.
Your DNS is not your problem, although you have some proxied records that could cause problems if you expect to use them with the protocols referenced by their names. Cloudflare does not proxy ftp, pop, or smtp. If you intend to use those host names with those protocols, you will need to set them to DNS Only.
Your mail server does not like your recipient email address. It does not exist on the receiving system. The mail server also does not like the sender email address. Based on the address formatting, it appears that your Sender Rewriting Scheme (SRS) is not working as intended.
It looks like you make use of a smarthost and possibly also hosted spam filtering capabilities from N-Able/SpamExerts. It might be worth reviewing your configuration of that platform with the vendor or your third-party integrator if you have one. This is not a problem that the Cloudflare Community can fix for you.
Unfortunately I don’t use either DirectAdmin or SRS, so I won’t have much to offer you on those two topics. My previous recommendation directing you to the DirectAdmin Forums was proposed because it seems likely to be a more effective resource for your particular situation, especially since your Cloudflare setup looks good (other than the proxied records for the ‘pop’ and ‘smtp’ hostnames which will yield undesirable results if used with non-HTTP protocols).
I’m not a big fan of running email services on web servers, nor do I endorse routing email to a destination MTA without a trip through a hosted spam filter first. I also find that forwarding email to external mailboxes in the age of DMARC is no longer an effective practice. All of this is just my opinion, and not the only way to do things, so you can give it consideration commensurate with what it cost you.
Good luck to you. I hope you are able to get this sorted quickly.