Loss Of Email - Avoiding It

[llama_thumper]

guys,

 

was wondering what the situation is concerning loss of email. what happens when a server is taken down for maintenance or my domain is migrated - do emails bounce or get held in a queue somewhere, by something? if so, by what?

 

recently i had some downtime, and noticed that emails were either getting lost completely (I sent one or two test messages to my domain address, from a non-domain address - both never arrived), or bounced (also sent from a non-domain address). is it not possible to somehow safeguard against this? bouncing emails is bad enough, but someone sending you something which you are never aware of (aka the black hole) is even worse. what precautions do TCH take against this, in migration or maintenance situations?

basically, what are the steps taken to ensure no email is lost?

[TCH-Thomas]

Usually it depends on the sending server. They usually try to send the email several times for a few days before its considered "Undelivereable". But again its up to the sending server from what I have learned.

[Deverill]

The mail sending protocols are set up such that if a server is unreachable the sending machine, or the last one along the route, stores up the email and tries again, usually in 24 to 48 hours and often 2 or 3 times, before throwing it out and bouncing a "could not deliver" message back to you.

 

Because of the way the internet works, I've never heard of a company with backup precautions against losing email in case of an outage. By the time you get everything switched over to a new machine (mail routes and such) the first server would be repaired and you'd still have lost certain emails were it not for the resend protocols.

[llama_thumper]

so there really is no sort of mail server at TCH that does queing of emails or anything of the sort?

 

the last time i had a migration, i was unable to find the mail server using outlook, if i recall correctly. then, once everything was back online, the email came trickling to me, ie all of those that were sent to me while the server was being migrated - first a couple, then a couple more, then a few more. if i would have waited then i could have gotten them all in one go - but what i'm trying to say is that i have this impression that something somewhere held these emails for me, while the server was being migrated. and considering that this was within 20-30 minutes, are you sure this was only just resends from SMTP servers?nothing on the incoming side?

[TCH-Bruce]

The servers that were sending the mail to you were holding the messages. Once the server routes were propagated after the migration those servers delivered the mail. That's the way it works.

[llama_thumper]

this is one of the email messages that bounced back to me when I sent it from a non-domain address, to my domain address, while the server was down. what does it say (in non-tech speak:))?

 

From: Mail Delivery System [Mailer-Daemon@mx.inode.at]Subject:Mail delivery failed: returning message to sender

Sent: Fri 27/10/2006 20:31

This message was created automatically by mail delivery software.

 

A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:

 

MyDomainAddressHere

SMTP error from remote mailer after RCPT TO:<MyDomainAddressHere>:

host MyDomainHere [72.18.159.15]: 550-Verification failed for <MyNonDomainAddressHere>

550-unrouteable mail domain "MYNONDOMAINADDRESSSERVERHERE"

550 Sender verify failed

 

------ This is a copy of the message's headers. ------

 

Return-path: <MyNonDomainAddressHere>

Received: from [85.125.145.68] (port=9899 helo=t40p1)

by smartmx-10.inode.at with esmtp (Exim 4.50)

id 1GdWTU-00014n-0V

for MyDomainAddressHere; Fri, 27 Oct 2006 20:30:36 +0200

From: "MyNameHere" <MyNonDomainAddressHere>

To: <MyDomainAddressHere>

Subject: test 1

Date: Fri, 27 Oct 2006 20:30:23 +0200

Message-ID: <000001c6f9f5$f7afb8b0$6900a8c0@t40p1>

MIME-Version: 1.0

Content-Type: multipart/alternative;

boundary="----=_NextPart_000_0001_01C6FA06.BB3888B0"

X-Mailer: Microsoft Office Outlook 11

X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2962

Thread-Index: Acb59fbTgPlI1k3KRIG2Z2eTDepc0g==

Edited October 30, 2006 by llama_thumper

[TCH-Bruce]

What it's telling you is it gave up trying to send to your domain address because it was failing to find it.

 

Depending on the service you sent the message through and how they have it set up would depend on how long or how many tries it would take before sending a message back to you that your message was not delivered.

[llama_thumper]

and because this service is set up to only try once, it gives up after one time, correct?

[TCH-Bruce]

Yes, that would be my take on it.