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"550 Access denied - Invalid HELO name" when emails are sent to certain domains

Hi,

I've noticed recently that when emails are being sent to certain domains from our Exchange Server they are failing a HELO check. Our emails our going through the Astaro SMTP proxy, all emails going out from the proxy are doing so via one IP address and I have checked that this IP address is not blacklisted anywhere. Also the the IP address associated with sending out email has a public DNS record.

Any help appreciated.

Thanks

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0 Ol Deda over 12 years ago

who is sending this error back to you ?
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0 Ol Deda over 12 years ago

I think your exchange is open relay and the UTM too
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0 turboizzy over 12 years ago in reply to Ol Deda

a few domains, one being hostgods.net. I can confirm that my exchange and Astaro proxy are not open relays.
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0 Ol Deda over 12 years ago

utm gives you this error? How exchange contacts other smtp servers with a conector or just directly
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0 turboizzy over 12 years ago in reply to Ol Deda

the error is bounce from their mail server
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0 BAlfson over 12 years ago

I think hostgods.net is having a problem. I telnetted there and didn't get a good response. Are you sure it's the remote MTA that's returning that error code and not the Astaro?

Cheers - Bob

Sophos UTM Community Moderator
Sophos Certified Architect - UTM
Sophos Certified Engineer - XG
Gold Solution Partner since 2005

MediaSoft, Inc. USA
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0 Ol Deda over 12 years ago

I'm sure like Bob said that response is from UTM. You have some wrong configuration in exchange
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0 turboizzy over 12 years ago in reply to Ol Deda

I agree with you Bob, seems like a dodgy domain. Not had any issues sending emails to any domains previously. Thanks for your feedback
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0 turboizzy over 12 years ago

They are basically rejecting the email from us. When I checked the SMTP logs it just says the email was bounced. Funnily enough this is one of two domains I have ever received this error from
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0 BrucekConvergent over 12 years ago in reply to turboizzy

OP, check your own mail setup out using mxtoolbox.com .... make sure you don't have any RDNS issues, etc.

It's a great tool. If your mail config passes the blacklist and SMTP tests on mxtoolbox.com, then the remote domains are the ones with the issue.

CTO, Convergent Information Security Solutions, LLC

https://www.convergesecurity.com

Sophos Platinum Partner

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Advice given as posted on this forum does not construe a support relationship or other relationship with Convergent Information Security Solutions, LLC or its subsidiaries. Use the advice given at your own risk.
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