Re: How getmail deals with delivery errors and with bounce e-mails

(Sorry, sendt directly by mistake, re-sending to mailing list)

On 04/11/2020 00:11, R. Diez wrote:
> 
>  > [...]
>> What you have set-up for email works like this (y is your domain, z is 
>> your ISP/RSPs domain, a is you at z):
>  > - Someone spits a message into the ether to x@y
>  > - eventually it ends up in the mailbox at a@z
> 
> I don't think that is the scenario I want. Let's rewind for a second. In 
> Europe you can buy a package for a few euros a month that includes 
> everything but the kitchen sink: a website, a domain name, mail, FTP, ...
> 
> The domain name you buy is yours. If you change provider, you can take 
> it with you. Or so I heard (I do not have much experience yet).
> 
> So, if my provider receives an e-mail for [email protected] , I then fetch 
> it with getmail, and it lands on my internal mail server, it is still 
> [email protected] (still the same domain).

If you are using Getmail to pull email from a mailbox, that mail was 
successfully delivered at the time it entered that mailbox.

That's it.  If it's accessible by Getmail, it's been delivered, sending 
a bounce causes problems.

> The provider's mail server may not reject the e-mail straight away, 
> because it will store it in the "catch all" mailbox, which accepts 
> anything. But my internal mail server can still generate some sort of 
> bounce e-mail later on, right? This is like a "I am on vacation" notice. 
> After all, if dovecot-lda can generate bounce e-mails, someone must have 
> deemed it necessary at that point in the delivery phase. The internal 
> mail server will only rely that bounce e-mail to my provider's SMTP 
> server, so it still goes out as legitimate e-mail from [email protected] .
> 
See above.  Once it's in a mailbox it's been delivered.

> You would of course try not to send too many bounce e-mails, just like 
> you do in the vacation case, by remembering the last sender addresses.
> 
Don't send bounce emails.  Particularly don't send them automatically.

>> If you want to tell people that "x@y" does not exists, deliver all 
>> unknown mail to a catch-all mailbox and do it manually.
> 
> OK. How would you do it? With some script that goes over some other 
> internal "catch all" mailbox? Have you got any examples at hand? 
> Preferably in Perl. 8-)
> 
By using my eyes.  Any automated back-scatter system will be identified 
as a SPAM generator, practically instantly.

>> You'll probably find that 99% is SPAM, and the other 1% are typos from 
>> people who won't respond anyway.
> 
> The 99 % spam should be filtered by my provider's mail server and not be 
> considered for automatic bouncing, so that is not an issue.
> 
Hahahaha!!  I have a bridge to sell you.

> Silently dropping e-mails from your prospective customers and/or friends 
> because they slightly misspelled your e-mail address is not very nice.
> 
It happens all the time.  Email is a "best effort" delivery system, 
nothing is guaranteed.

So you use a catch-all mailbox and review it every day or two, just like 
those of us who are running full internet-connected MTAs review the logs.

If you see it happen often enough, you add an alias for the most common 
stuff-ups.  (And yes, it can be a bugger when you have 5000+ *valid* 
email addresses, but it's part of the job.)

I've noticed that Larry Fahnoe has posted a good explanation of *why* 
you shouldn't do wrong things with email, so I will just repeat:

Don't send bounce emails.

	Cheers,
		Gary	B-)