As explained at #670 (comment), I've had a message fail to reach a recipient of mine, which was luckily caught by app.addy.io/failed-deliveries (despite me having addy.io set as an excluded domain). However, this has made me realise that having a middleman just pushes the problem back:

Yes that banner is added when a message looks like spam or has a DMARC policy of none/quarantine that has failed. But if the domain had a DMARC policy of reject and it fails then it will be rejected.

Unfortunately, the functionality to verify that AnonAddy isn't blocking anything I care about doesn't exist, but is possible to provide (as #670 (reply in thread) explains):

I may be able to parse the mail logs in order to also show inbound rejections in the future.

Consequently, I'd like to be able to see inbound rejections (alongside the aforementioned existent outbound rejection list) to ensure that Addy isn't blocking mail from senders that I care about.