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I am not receiving emails in my hotmail account from one particular address. (They're not being filtered out as junk mail, before you ask)

I have been given the suggestion that they are being blocked by my firewall. Is this possible? I would have thought it couldn't be, since it is web mail and the emails only ever exist on Microsoft's server.

I reckon the problem exists at the sender's end, but they are adamant it doesn't since they can send to everyone else ok. Surely, it can't be a problem at my end, right?

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The sender probably does not have a PTR record properly set up. Hotmail will drop all such e-mail with no notice. If you post the domain of the sender (I don't need the entire e-mail address), I can do an nslookup and check for you for certain. –  KCotreau Jun 14 '11 at 14:42
    
Ok. The domain is "@news.groupon.co.uk". –  Urbycoz Jun 14 '11 at 14:56
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"I have been given the suggestion that they are being blocked by my firewall." -- for any reasonable definition of "my" and "firewall", that suggestion is nonsensical. There's just no mechanism for anything like that to move a message into your junk folder. –  Mike Renfro Jun 14 '11 at 15:23
    
@ Mike. Good, that's what I told 'em. –  Urbycoz Jun 14 '11 at 15:35
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up vote 4 down vote accepted

Here is the nslookup results. To be honest, I saw groupon, and thought there is no way such a big company would not be set up right, but now I am not so sure:

Microsoft Windows [Version 6.1.7601] Copyright (c) 2009 Microsoft Corporation. All rights reserved.

C:>nslookup server 199.191.128.103 Default Server: rbru.br.rs.els-gms.att.net Address: 199.191.128.103

set q=mx groupon.co.uk Server: rbru.br.rs.els-gms.att.net Address: 199.191.128.103

Non-authoritative answer: groupon.co.uk MX preference = 10, mail exchanger = groupon-1.mx.heinlein-support.de groupon.co.uk MX preference = 20, mail exchanger = groupon-3.mx.heinlein-support.de groupon.co.uk MX preference = 10, mail exchanger = groupon-2.mx.heinlein-support.de

I pinged groupon-1.mx.heinlein-support.de in another window, and it came back as 91.198.250.10

set q=ptr 91.198.250.10 Server: rbru.br.rs.els-gms.att.net Address: 199.191.128.103

Non-authoritative answer: 10.250.198.91.in-addr.arpa name = mx1.heinlein-support.de

The fact is that that unless they are doing something I don't understand the return on that PTR record, mx1.heinlein-support.de, should match the name of the MX 10 record, or the mail will be dropped by Hotmail.

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Interesting. So the bottom line is that Groupon have probably not got their email configured correctly. Many thanks for your help. –  Urbycoz Jun 14 '11 at 15:20
    
As far as I can see, and I do A LOT of e-mail for a living. I suppose it is possible they have some funky DNS setup I do not have full knowledge of, I installed Exchange 2010 on two continents this week for a company via the Internet actually. –  KCotreau Jun 14 '11 at 15:43
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