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Is Cloudflare a cheapo VPS? It is a cheap VPS, but it would still be nice if there was a way to know (not assume) beforehand. > 550 5.7.1 Unfortunately, messa

Is Cloudflare a cheapo VPS? It is a cheap VPS, but it would still be nice if there was a way to know (not assume) beforehand. > 550 5.7.1 Unfortunately, messages from [IP ADDRESS] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). > Your IP(s) qualify for conditional mitigation. Still blocked. The system is working as expected.

jeffbee 3mo ago
I would simply like to point out that 550 at SMTP time is not a bounce.
- doubled112 3mo ago
  You get an email bounce back with an error code in it. Is there some other definition I'm unaware of? Wait, that is probably from the local mailer, and otherwise the sender may never know about the rejected messages.
- b112 3mo ago
  5xx are bounces, a perm failure. 4xx error codes are temp (retry) errors.
  - jeffbee 3mo ago
    Incorrect. A bounce is a delivery status notification generated by a mailer after it has already accepted a message for delivery. A 5xx permanent error is a refusal to accept the message in the first place.
    - TZubiri 3mo ago
      Is this standarized terminology in some RFC like SMTP? Or is it presumably some well established folk lingo?
      - b112 3mo ago
        They're referring to the bounced notification message, not the fact that the mail bounced. Verb and noun. A 5xx is a bounce, and results in a bounced email message. Variances always abound, but I'll stick with my 30 year old terminology, and it is correct.
        jeffbee 3mo ago
        That's fair with regards to your statement, but "doubled112" assigned the agency to Microsoft, saying that "Microsoft bounces" their traffic, which is demonstrably not what is happening.
        b112 3mo ago
        It is what's happening, as I've described. A 5xx is a bounce. You don't agree with my terminology, but we're not disagreeing on what's happening. In this case, as per my dictionary, 'rejected' and 'bounced' are synonyms. If this was me, and my MTA hitting this Microsoft server, my MTA/server would see the bounce(5xx), then my MTA/server would generate a bounce message(email) which I'd receive in my inbox. The bounce message is a result of the bounce. The action/cause is the bounce/reject 5xx. How can you have a bounce message, without a bounce happening? Again, you don't agree with this terminology, and that's fine. But I'm not pulling this out of a random hat, it's 30+ year old terminology that I've used with endless people locally and online. That doesn't mean your view is wrong, we may just be running into local variances in lingo. There are all sorts of edge cases in our compute discourse. I ran into a company where they didn't use initialisms to discuss daemons/protocols, but treated them as acronyms. Of course, they didn't really discuss such things often. So when discussing smtp, they'd pronounce it 'sim-tee'. Of course, sntpd, smtpd, snmpd, and others are all pronunced 'sim-tee', which makes for a fun meeting. Think of it as 'I am groot' taken too far. For prudence, I kept enforcing initialisms, which of course resolved this. Anyhow! Point is, well.. not really sure except info.
      - turpentine 3mo ago
        jeffbee isn't offering any explanation, maybe because it's obvious to them they don't think they need to, or something like that... so I'll volunteer one. If you send an email, your client would talk to your local MTA (i.e. the SMTP server you own or are authorised to relay mail through, e.g. ISP). The local MTA usally just accepts the email to insert it into a queue for attempting delivery. When your MTA processes the queue, and talks to another and gets 5xx or 4xx response, your MTA will generate a "bounce" (non-delivery report) email that lands in your inbox with the details of the response it received. So jeffbee is correct that when the local MTA gets a 5xx or 4xx response code in the SMTP session with target MTA, that /the response code is not a bounce/. Microsoft responding with 5xx or 4xx in the SMTP session, they are not bouncing the email. They are refusing to accept delivery. For Microsoft to "bounce every email" from the original parent commenter, it would have accept each email first, and then use the return path address of each email accepted to send a bounce email asynchronously, i.e. the bounce is not part of the original session. If a MTA talks to another MTA who accepts a message for delivery, they can then bounce the email at any later point via the address specified in the return path header. Why? Maybe incoming email is queued and scanned, because it would take too long to determine if it passes secondary rules when it's initially being accepted. Given how this works, you could take an email inbox you received a year ago, or five... and send an email with whatever content to the return path address, and you have "bounced" the original email.
inigyou 3mo ago
Cloudflare is one of the shadiest hosts around, almost as bad as the big three clouds.
TZubiri 3mo ago
You can't have the cake and eat it too. Either you use cheap infrastructure that attackers can buy by the bulk for sybil attacks. Or you pay a reasonable price for a slice of an IP block that doesn't share its reputation with elcheapos.
- doubled112 3mo ago
  No disagreement here. I had never planned to use it for email, but I was bored and I already had it when I got an idea.

jeffbee 3mo ago

I would simply like to point out that 550 at SMTP time is not a bounce.

doubled112 3mo ago
You get an email bounce back with an error code in it. Is there some other definition I'm unaware of? Wait, that is probably from the local mailer, and otherwise the sender may never know about the rejected messages.
b112 3mo ago
5xx are bounces, a perm failure. 4xx error codes are temp (retry) errors.
- jeffbee 3mo ago
  Incorrect. A bounce is a delivery status notification generated by a mailer after it has already accepted a message for delivery. A 5xx permanent error is a refusal to accept the message in the first place.
  - TZubiri 3mo ago
    Is this standarized terminology in some RFC like SMTP? Or is it presumably some well established folk lingo?
    - b112 3mo ago
      They're referring to the bounced notification message, not the fact that the mail bounced. Verb and noun. A 5xx is a bounce, and results in a bounced email message. Variances always abound, but I'll stick with my 30 year old terminology, and it is correct.
      - jeffbee 3mo ago
        That's fair with regards to your statement, but "doubled112" assigned the agency to Microsoft, saying that "Microsoft bounces" their traffic, which is demonstrably not what is happening.
        b112 3mo ago
        It is what's happening, as I've described. A 5xx is a bounce. You don't agree with my terminology, but we're not disagreeing on what's happening. In this case, as per my dictionary, 'rejected' and 'bounced' are synonyms. If this was me, and my MTA hitting this Microsoft server, my MTA/server would see the bounce(5xx), then my MTA/server would generate a bounce message(email) which I'd receive in my inbox. The bounce message is a result of the bounce. The action/cause is the bounce/reject 5xx. How can you have a bounce message, without a bounce happening? Again, you don't agree with this terminology, and that's fine. But I'm not pulling this out of a random hat, it's 30+ year old terminology that I've used with endless people locally and online. That doesn't mean your view is wrong, we may just be running into local variances in lingo. There are all sorts of edge cases in our compute discourse. I ran into a company where they didn't use initialisms to discuss daemons/protocols, but treated them as acronyms. Of course, they didn't really discuss such things often. So when discussing smtp, they'd pronounce it 'sim-tee'. Of course, sntpd, smtpd, snmpd, and others are all pronunced 'sim-tee', which makes for a fun meeting. Think of it as 'I am groot' taken too far. For prudence, I kept enforcing initialisms, which of course resolved this. Anyhow! Point is, well.. not really sure except info.
    - turpentine 3mo ago
      jeffbee isn't offering any explanation, maybe because it's obvious to them they don't think they need to, or something like that... so I'll volunteer one. If you send an email, your client would talk to your local MTA (i.e. the SMTP server you own or are authorised to relay mail through, e.g. ISP). The local MTA usally just accepts the email to insert it into a queue for attempting delivery. When your MTA processes the queue, and talks to another and gets 5xx or 4xx response, your MTA will generate a "bounce" (non-delivery report) email that lands in your inbox with the details of the response it received. So jeffbee is correct that when the local MTA gets a 5xx or 4xx response code in the SMTP session with target MTA, that /the response code is not a bounce/. Microsoft responding with 5xx or 4xx in the SMTP session, they are not bouncing the email. They are refusing to accept delivery. For Microsoft to "bounce every email" from the original parent commenter, it would have accept each email first, and then use the return path address of each email accepted to send a bounce email asynchronously, i.e. the bounce is not part of the original session. If a MTA talks to another MTA who accepts a message for delivery, they can then bounce the email at any later point via the address specified in the return path header. Why? Maybe incoming email is queued and scanned, because it would take too long to determine if it passes secondary rules when it's initially being accepted. Given how this works, you could take an email inbox you received a year ago, or five... and send an email with whatever content to the return path address, and you have "bounced" the original email.

inigyou 3mo ago

Cloudflare is one of the shadiest hosts around, almost as bad as the big three clouds.

TZubiri 3mo ago

You can't have the cake and eat it too. Either you use cheap infrastructure that attackers can buy by the bulk for sybil attacks. Or you pay a reasonable price for a slice of an IP block that doesn't share its reputation with elcheapos.

doubled112 3mo ago
No disagreement here. I had never planned to use it for email, but I was bored and I already had it when I got an idea.