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> email is a reliable transport I mean, it is. Either you email will be delivered successfully, or you get a message that it couldn't be delivered. If disappea

> email is a reliable transport I mean, it is. Either you email will be delivered successfully, or you get a message that it couldn't be delivered. If disappears without trace, then most likely system administrator has manually deleted it

keanpedersen 4y ago
..or you are sending to a Microsoft-hosted email like @outlook.com, @hotmail.com or @live.com and they have decided that your sending server is spammy. In that case they will silently drop your mail.
- ryan-c 4y ago
  My experience with this as been more that they will silently drop email if you haven't been sending enough legitimate email for them to classify you as non-spammy. How do you bootstrap that? I have no idea.
  - account42 4y ago
    IME problems with Microsoft have been entirely with the using netblock-based blacklists that you can't do anything to prevent from ending up on unless you buy a whole /24. Thankfully, I don't really need to care about deliverability to MS so I can consider this their problem.
comboy 4y ago
Just the fact that the message itself is an e-mail should be enough to see some issues with your reasoning.
dspillett 4y ago
Not even remotely true. Not even the first hop from your local MTA can be trusted in that regard, it may accept the message and just immediately bin it, it might accept it but queue it for further verification and not bother sending you a message back telling you this had happened, etc. Between your MTA and the receiving mailbox there could be several hops, any of which might silently send your message to /dev/null. And that is without considering the same issues with the MUA, assuming your message is for human consumption and your aren't using SMTP to communicate between automated agents) at the other end having it's own spam/junk/other filtering (though I suppose you could consider that later part to not be email transport begin unreliable, i.e. if you consider successful transport to be "the user saw it" or "their mail server time their MUA it existed"). The only reliable bit of email transfer is the little bit you have full control over, the local MTA. Even then, if you are in a shared hosting environment where you don't control that yourself this could still silently reject your messages (a consideration you might need to make if publishing software others may self-host).
- teddyh 4y ago
  E-mail is a reliable transport. Claiming it is not is like claiming that TCP is not a reliable transport, just because extreme packet loss exists, and firewalls can play any games they like. Yes they can, but that does not make TCP an unreliable transport.
  - dspillett 4y ago
    I suppose that SMTP can be considered a reliable transport if you trust all MTAs and MUAs to properly implement the specs. But email more generally is certainly not IMO.
    - account42 4y ago
      Nothing is a reliable transport if you can't trust the operators to follow the specs. In practice, E-Mail is quite reliable, even in situations where other systems drop messages. For example, you don't need to worry about dropped messages from any downtime of reasonable length (e.g. for system upgrades) because well-behaved MTAs will retry later - this is the entire basis for greylisting.
- citrin_ru 4y ago
  A good behaving spam filter should either returns 5xx/4xx during an SMTP transactions or send a bounce. Returning 250 and then dropping a message without a bounce is a very bad idea but luckily it is not very common - no known to me opensource MTA does this by default and some make it hard to configure this (mis)behavior even if an administrator wants it. Unfortunately email is very centralized nowadays and companies known for bad behavior in general (and deleting emails without telling anyone in particular) now control too many mailboxes.
blacklion 4y ago
Never was ghost-banned by GMail? You are lucky.

keanpedersen 4y ago

..or you are sending to a Microsoft-hosted email like @outlook.com, @hotmail.com or @live.com and they have decided that your sending server is spammy. In that case they will silently drop your mail.

ryan-c 4y ago
My experience with this as been more that they will silently drop email if you haven't been sending enough legitimate email for them to classify you as non-spammy. How do you bootstrap that? I have no idea.
- account42 4y ago
  IME problems with Microsoft have been entirely with the using netblock-based blacklists that you can't do anything to prevent from ending up on unless you buy a whole /24. Thankfully, I don't really need to care about deliverability to MS so I can consider this their problem.

comboy 4y ago

Just the fact that the message itself is an e-mail should be enough to see some issues with your reasoning.

dspillett 4y ago

Not even remotely true. Not even the first hop from your local MTA can be trusted in that regard, it may accept the message and just immediately bin it, it might accept it but queue it for further verification and not bother sending you a message back telling you this had happened, etc. Between your MTA and the receiving mailbox there could be several hops, any of which might silently send your message to /dev/null. And that is without considering the same issues with the MUA, assuming your message is for human consumption and your aren't using SMTP to communicate between automated agents) at the other end having it's own spam/junk/other filtering (though I suppose you could consider that later part to not be email transport begin unreliable, i.e. if you consider successful transport to be "the user saw it" or "their mail server time their MUA it existed"). The only reliable bit of email transfer is the little bit you have full control over, the local MTA. Even then, if you are in a shared hosting environment where you don't control that yourself this could still silently reject your messages (a consideration you might need to make if publishing software others may self-host).

teddyh 4y ago
E-mail is a reliable transport. Claiming it is not is like claiming that TCP is not a reliable transport, just because extreme packet loss exists, and firewalls can play any games they like. Yes they can, but that does not make TCP an unreliable transport.
- dspillett 4y ago
  I suppose that SMTP can be considered a reliable transport if you trust all MTAs and MUAs to properly implement the specs. But email more generally is certainly not IMO.
  - account42 4y ago
    Nothing is a reliable transport if you can't trust the operators to follow the specs. In practice, E-Mail is quite reliable, even in situations where other systems drop messages. For example, you don't need to worry about dropped messages from any downtime of reasonable length (e.g. for system upgrades) because well-behaved MTAs will retry later - this is the entire basis for greylisting.
citrin_ru 4y ago
A good behaving spam filter should either returns 5xx/4xx during an SMTP transactions or send a bounce. Returning 250 and then dropping a message without a bounce is a very bad idea but luckily it is not very common - no known to me opensource MTA does this by default and some make it hard to configure this (mis)behavior even if an administrator wants it. Unfortunately email is very centralized nowadays and companies known for bad behavior in general (and deleting emails without telling anyone in particular) now control too many mailboxes.

blacklion 4y ago

Never was ghost-banned by GMail? You are lucky.