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Intermittent Error that users get when sending email to my personal domain/address. What does this mean?

Posted on 2008-10-08
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Last Modified: 2012-06-27
I have my own domain which I use for email.
I manage my DNS settings through www.zoneedit.com and all email is forwarded to a Gmail account I have.

Lately I have had some people say that their emails bounce back when they try to send me something.

Here is the error:
550 5.1.1 <me@MyDomain.com>: Recipient address rejected: User unknown in virtual alias table

I'm unable to find out what this means. Any idea what is wrong?
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Question by:Zeropoint_007
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by:Chris Dent
ID: 22673073

Do you have an anti-spam package?

Do you have more than one server listed in your MX Record?

That kind of error normally occurs when someone tries to send to a recipient the server doesn't believe exists.

Chris
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by:Zeropoint_007
ID: 22673475
>>Chris-Dent:
>>Do you have an anti-spam package?

Nope. Gmail has it's own Spam filtering but I always check it.

>>Do you have more than one server listed in your MX Record?

I don't have any servers setup in MX Record.
I MailForwards setup to forward set email addresses forwarded to my Gmail.

I don't think I can setup Gmail's servers in MX Record. Correct me if I'm wrong.

>>That kind of error normally occurs when someone tries to send to a recipient the server doesn't believe exists

Hmmm, thanks. That makes sense but how do I fix this?
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by:Steve
ID: 22674324
yeah, we see this a lot, but its 99.9% because the user has misspelt the end users email address..

as chris said, the server dosent believe the recipient exists on that email address. so check the spelling on the bounced mail..

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by:Chris Dent
ID: 22676441

Checking the spelling is a really good idea, that is exceptionally common :)

> That makes sense but how do I fix this?

That's a really difficult question to answer. It depends very much on what system is actually handling the mail, and exactly where it's bouncing.

The NDR message states enough to begin with, it tells you the last system to successfully handle the message, and the error it received when it was delivered onwards.

If I were looking after the sender mail system I would probably check the SMTP logs to see exactly where I attempted to deliver the message.

If I were the recipient I would be looking at the SMTP logs to see if it even got as far as my server.

In both cases I would test all servers listed in the MX record. It is possible that only one server exhibits the problem, and that we see intermittent delivery because of it.

Chris
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Author Comment

by:Zeropoint_007
ID: 22678781
>>PsychoFelix:
>>yeah, we see this a lot, but its 99.9% because the user has misspelt the end users email address..
>>as chris said, the server dosent believe the recipient exists on that email address. so check the
>>spelling on the bounced mail..

Yup, I did that. The spelling is fine.

>>Chris-Dent:
>>That's a really difficult question to answer. It depends very much on what system is actually handling
>>the mail, and exactly where it's bouncing.
>>The NDR message states enough to begin with, it tells you the last system to successfully handle the
>>message, and the error it received when it was delivered onwards.
>>If I were looking after the sender mail system I would probably check the SMTP logs to see exactly
>>where I attempted to deliver the message.
>>If I were the recipient I would be looking at the SMTP logs to see if it even got as far as my server.
>>In both cases I would test all servers listed in the MX record. It is possible that only one server
>>exhibits the problem, and that we see intermittent delivery because of it.

Thanks but there seems to be a misunderstanding here. Or maybe I don't understand this properly.
Both ends (sender and recipient) are using public emails systems.
So I don't have access to server/SMTP logs etc.

The setup I have is very simple. There are no MX records, just a simple forward rule for any mail with my domain name to be forwarded to my Gmail address.

I am thinking of 2 possible reasons for my problem:
1) My domain name is not propagating properly and some DNS servers don't recognize it.

2) Recently (past couple months) I remember reading about DNS poisoning attacks. Perhaps recent security measures to counter this is causing DNS servers to think my domain name is not "legitimate"?

Maybe I'm way off. Let me know if I am.
Thanks for the advice so far.
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Chris Dent earned 500 total points
ID: 22678904

It's more likely that we're approaching it from different angles :)

> There are no MX records, just a simple forward rule for any mail with my
> domain name to be forwarded to my Gmail address

Something must answer on the SMTP level for that to occur. So that would make three systems:

Sender -> Forwarder -> Recipient

That Forwarder doesn't do anything but act on a rule is irrelevant.

One of the servers receiving the message, Forwarder or Recipient, is performing recipient validation. That is, it is checking the to address on the mail and rejecting it if it can't find a match.

That takes us out of the DNS realm entirely unless the server handling the message is incorrectly set.

We should be able to determine which it is from the NDR. If the server quoted on the NDR belongs to Sender then the Forwarder is at fault. If it belongs to Forwarder then the Recipient is at fault.

If an MX record isn't defined the A record bound to the domain name itself will be used. e.g.

If this returns nothing:

nslookup -q=mx domain.com

This will be used:

nslookup -q=a domain.com

That doesn't leave us in a very good place. If you don't administer any of the systems then you simply cannot check and fix this. Calls would have to be raised with those that do administer the systems to do that.

Chris
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Author Closing Comment

by:Zeropoint_007
ID: 31504425
Excellent! Thanks for the explanation. I think I may know where things went wrong.
Here: nslookup -q=a domain.com
Basically my domain points to my PC IP address where there is no email server and since there are no MX records, I'm guessing this is where the confusion comes up.
It seems likely the problem is on my end.
Thanks again.
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