Email routing insanity

I’ve been pulling my hair out with Cloudflares email routing, which seem highly determined, not to deliver mails to my email server no matter what I do.

That said, the destination mailbox checks out good, perfect 10 w/ all DNS records glowing green.
Likewise, I can send to this mailbox using; hotmail, gmail, mxroute, etc, and without any issues whatsoever.

But not Cloudflare, as it completely refuses to send to any email on that mail server no matters what - returning:

upstream ( error: failed to initalize: Unknown error: permanent error (550): Verification failed for <…com>Invalid SRS recipient addressSender verify failed

That being said, the only possible scenario that I can think-of at this stage, is that Cloudflare email routing makes use of blocklist type records, and is therefore refusing any and all requests to said email server(domain).

Otherwise, I have no idea what else to consider, given that the destination email checks out, and that the service is simply refusing to process anything to it - though it should be added, that the routing system has no issues sending the authorization mail to said destination email :confused:

That looks like your mail server performs Sender Verification and rejects the forwarded emails based on the result.

Apparently not, as the email routing starting working without any changes made :frowning :frowning: