Dear all
I recently spent several days trying to figure out why a customer was getting blacklisted on CBL after several years of unchanged configuration.
It turned out that CBL have suddenly and arbitrarily decided to blacklist any mail server that answers with HELO that looks like a dynamic address, even if it is not.
Some time ago e.g. 2 years+, my ISP recommended that I set the FQDN of my Exchange email server to xxx.demon.co.uk which is what reverse DNS will produce when looking up the IP. Now it has been changed back to mailgate.xxxx.ltd.uk.
FYI they define something to be a dynamic address if the name looks like the address the ISP has your IP resolving to, whether or not the IP address is static (as in these cases) or dynamic.
So to avoid this, your mail server's HELO string must be something different to the style of address used by ISPs.
But it does highlight a number of issues - not least, blacklists arbitrarily taking decisions without thinking through the consequences.
Greylisting is another problem area - I have found some admins who have implemented this with settings that ensure that a standard Exchange server will never get through because the settings are mutually exclusive.
All of these are kludges - it would be much better if we had all legitimate mailservers adopting SPF
Sorry if some of you think this is off topic, but I thought it worth alerting people to the style of mailserver name getting you blacklisted.
Tony Gore
email tony@aspen.uk.com
tel +44-1278-761000Â FAX +44-1278-760006Â GSM +44-7768-598570
URL: www.aspen.uk.com
Aspen Enterprises Limited
Registered in England and Wales no. 3055963 Reg.Office Aspen House, Burton Row, Brent Knoll, Somerset TA9 4BW. UK
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I recently spent several days trying to figure out why a customer was getting blacklisted on CBL after several years of unchanged configuration.
It turned out that CBL have suddenly and arbitrarily decided to blacklist any mail server that answers with HELO that looks like a dynamic address, even if it is not.
Some time ago e.g. 2 years+, my ISP recommended that I set the FQDN of my Exchange email server to xxx.demon.co.uk which is what reverse DNS will produce when looking up the IP. Now it has been changed back to mailgate.xxxx.ltd.uk.
FYI they define something to be a dynamic address if the name looks like the address the ISP has your IP resolving to, whether or not the IP address is static (as in these cases) or dynamic.
So to avoid this, your mail server's HELO string must be something different to the style of address used by ISPs.
But it does highlight a number of issues - not least, blacklists arbitrarily taking decisions without thinking through the consequences.
Greylisting is another problem area - I have found some admins who have implemented this with settings that ensure that a standard Exchange server will never get through because the settings are mutually exclusive.
All of these are kludges - it would be much better if we had all legitimate mailservers adopting SPF
Sorry if some of you think this is off topic, but I thought it worth alerting people to the style of mailserver name getting you blacklisted.
Tony Gore
email tony@aspen.uk.com
tel +44-1278-761000Â FAX +44-1278-760006Â GSM +44-7768-598570
URL: www.aspen.uk.com
Aspen Enterprises Limited
Registered in England and Wales no. 3055963 Reg.Office Aspen House, Burton Row, Brent Knoll, Somerset TA9 4BW. UK
-------------------------------------------
Sender Policy Framework: http://www.openspf.org
Modify Your Subscription: http://www.listbox.com/member/
Archives: https://www.listbox.com/member/archive/1020/=now
RSS Feed: https://www.listbox.com/member/archive/rss/1020/
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