> Is there actually a "big tech" email provider that accepts a message with a 2xx SMTP code and then deletes it?
Agreed, that is really broken behavior. Once you accept mail for delivery, it should be treated as a contract to deliver that mail. Rejects during SMTP conversation are fine as they notify the sender and do not generate backscatter.
I have heard complaints that Microsoft's hosted mail offerings accept then silently delete mail. It is somewhat believable, as MS Exchange server would respond 2xx for any message to any (including non-existent) destination address and later spam the possibly spoofed sender with bounce messages. Maybe MS has broken behavior like this in their hosted offerings too? And, rather than fix their software, they silently delete mail since they have finally learned that backscatter is a bad thing?
And, MS o365 allows 'delete' as an option for the centralized spam rules maintained by the admin. These mails are accepted 2xx then silently deleted.
MS does other questionable things on their 'free' hosted offerings to mitigate their abysmal spam filtering. I have a couple burner @outlook.com addresses, and they no longer receive any mail reliably from any sender. MS provides the user a place to whitelist senders and domains, but after wasting a bunch of time whitelisting domains, mail still is marked spam. "Junk" is effectively the inbox on those accounts.
Disclaimer: experience is dated, from a past job, running Postfix MTAs for a large organization and dealing with / mitigating MS issues, but never directly involved with any MS stuff.
Agreed, that is really broken behavior. Once you accept mail for delivery, it should be treated as a contract to deliver that mail. Rejects during SMTP conversation are fine as they notify the sender and do not generate backscatter.
I have heard complaints that Microsoft's hosted mail offerings accept then silently delete mail. It is somewhat believable, as MS Exchange server would respond 2xx for any message to any (including non-existent) destination address and later spam the possibly spoofed sender with bounce messages. Maybe MS has broken behavior like this in their hosted offerings too? And, rather than fix their software, they silently delete mail since they have finally learned that backscatter is a bad thing?
And, MS o365 allows 'delete' as an option for the centralized spam rules maintained by the admin. These mails are accepted 2xx then silently deleted.
MS does other questionable things on their 'free' hosted offerings to mitigate their abysmal spam filtering. I have a couple burner @outlook.com addresses, and they no longer receive any mail reliably from any sender. MS provides the user a place to whitelist senders and domains, but after wasting a bunch of time whitelisting domains, mail still is marked spam. "Junk" is effectively the inbox on those accounts.
Disclaimer: experience is dated, from a past job, running Postfix MTAs for a large organization and dealing with / mitigating MS issues, but never directly involved with any MS stuff.