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My company has recently purchased a VPS for email and webhosting. I am not an expert on email authentication but here is my story.

After the VPS was purchased we started receiving bouncebacks with the error message from hotmail.com:

550 SC-001 (COL0-MC1-F10)
Unfortunately, messages from 205.234.204.81 weren't sent. Please contact
your Internet service provider since part of their network is on our block
list. You can also refer your provider to
http://mail.live.com/mail/troubleshooting.aspx#errors

After doing research on the issue I have tried to join hotmail Sender ID program. I also added an SPF to my domain (not sure if it is correct)

v=spf1 a mx ip4:205.234.20x.xx a:xxserver.com mx:xxserver.com ?all

After petitioning the Hotmail blacklist by filling out their form, I am still on their blacklist. Many of our customers are Hotmail accounts and this is becoming a big issue for us. I am not sure if my rDNS is correct, the SPF record or what is the problem.

I am aware that I may be leaving out some information, I am new to the email server administration so I will post what I can to make this easier. Thank you!

I have seen other threads on here and tried to follow their instruction to no avail.. and I did not want to resurrect an old thread.

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I'd ask your VPS provider for a new IP address. –  ceejayoz Jan 17 '12 at 16:31
    
Ask owner of OP-block (VPS-hoster) initiate delisting process on Hotmail - you can do nothing –  Lazy Badger Jan 17 '12 at 16:43
2  
"I have tried to join hotmail Sender ID program" SenderID is a technology you implement on your server, nothing to do with Hotmail. Your SPF record will be ignored by many (if not most) servers because it's got "?all" on the end (which most mail admins interpret (fairly or not) as "I don't know what I'm doing and put minimal effort into this". rDNS appears to be working. Side note: that's a weird name for a mail server. You'll have to ask HostForWeb to get their netblock delisted if it's the whole block. If they're well known for hosting spam servers it's not happening though. –  Chris S Jan 17 '12 at 16:43
    
the actual IP is 205.234.204.81 and 205.234.204.83 diamondbackserver.com .. I have contacted hostforweb to remove the IP from blacklist or give me a new one. Hope this works, thanks for explaining things a little better. –  DBIT Jan 19 '12 at 13:57
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2 Answers

If you are on Hotmail's blacklist then the only way you are going to get off it is to get them to remove you, or get a new IP.

If your IP is blacklisted and you don't believe it's of your doing, then you need to go back to your ISP and ask for a new one.

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It's not your IP's reputation. Senderscore get some of their reputation information from Hotmail and they think your IP address is clean: https://www.senderscore.org/lookup.php?lookup=205.234.204.81

SenderBase think you're clean too: http://www.senderbase.org/senderbase_queries/detailip?search_string=205.234.204.81

The error message in your question says:

part of their network is on our block list.

So it's not your IP address but too many of the other IP addresses your hosting provider owns that are the problem. (Assuming that the error message from Hotmail is accurate.)

Talk to your hosting provider. If they can't fix their IP address space reputation in a reasonable time frame, either get a new hosting provider, a third-party mail relay or use your hosting provider's mail relay (if it has a reasonable reputation).

As for reverse DNS, the forward and reverse do match each other. I don't know what your HELO looks like but as long as it matches the forward DNS it should be fine.

With SPF, -all is the best choice. A lot of people choose ~all thinking that if they screw up, at least the messages will still be delivered but this is erroneous thinking. With -all you get a bounce to let you know that your SPF is not configured properly. With ~all your emails get silently put in the recipient's junk folder.

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HELO does match. –  Chris S Jan 17 '12 at 19:41
    
Thank you, I switched the SPF to -all. I am also writing an email to hostforweb to fill out the msn blacklist form. If they fail to fix this I will settle for another VPS provider. Thanks for your responses! –  DBIT Jan 19 '12 at 13:54
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