Like many others who have been using the Internet for a very long time, I have a lot of email addresses. From the well known cloud provides like Google and Microsoft, to my own self-hosted Postfix server. In order to maintain my sanity and keep my emails to a single location, I use a complex array of forwarding rules from one email to the next so that all my messages end up in one place, regardless of what address people use to contact me. But as a result of this, I came up with some interesting observations.
It's well known that cloud email services use block lists and patterns in order to identify spam, that's why we have junk folders. But I found out that some services will also silently drop emails. Apple iCloud seems particularly bad at this. Because I'm running my own server and forwarding emails to iCloud, I see the log files and routinely spot this type of entries:
Nov 28 05:49:16 gwendis postfix/smtpd: 83A0B1842186: client=mta.e.walmart.ca[126.96.36.199] Nov 28 05:49:16 gwendis postfix/cleanup: 83A0B1842186: message-id=<firstname.lastname@example.org> Nov 28 05:49:16 gwendis postfix/qmgr: 83A0B1842186: from=<bounce-116078_HTMLemail@example.com>, size=52959, nrcpt=2 (queue active) Nov 28 05:49:16 gwendis postfix/local: 83A0B1842186: to=<firstname.lastname@example.org>, relay=local, delay=0.32, delays=0.31/0.01/0/0, dsn=2.0.0, status=sent (delivered to mailbox) Nov 28 05:49:19 gwendis postfix/smtp: 83A0B1842186: to=<email@example.com>, orig_to=<firstname.lastname@example.org>, relay=mx2.mail.icloud.com[188.8.131.52]:25, delay=3.1, delay s=0.31/0.01/0.31/2.5, dsn=5.7.1, status=bounced (host mx2.mail.icloud.com[184.108.40.206] said: 550 5.7.1 [CS01] Message rejected due to local policy. Please visit https://support.apple.com/en-us/HT204137 (in reply to end of DATA command)) Nov 28 05:49:19 gwendis postfix/bounce: 83A0B1842186: sender non-delivery notification: 91C1618617EE Nov 28 05:49:19 gwendis postfix/qmgr: 83A0B1842186: removed
This is an email from Walmart, assuredly advertisement, that was silently blocked with a 550 error code with a message saying Message rejected due to local policy. But the thing is, the recipient will never see this email. It won't show up in the junk folder, or anywhere. And because this is a reply to a forwarder, the sender won't see it either. This message was silently blocked and no one will know about it.
The iCloud policy says this:
We track a sender's reputation using various mechanisms, such as IP and domain reputations, content checks, and user feedback. Then we make our filtering decisions.
Basically they can decide to reject messages any time they want. I see this type of rejection about once or twice a week. Usually Apple is blocking blatant spam or malware, but sometimes it's well known companies like Walmart that get blocked. I personally don't care to see their adverts, but I would rather it end up in my junk folder so that I can make the decision, instead of Apple blocking it outright.
Is it okay for email services to silently reject some emails that were destined for you? Since the vast majority of users will never know about this, it's unlikely to change.