Just got a file attachment from a trusted source with the extension.zm9 & I am unable to open it. I've checked all my system settings including OE6, ZoneAlarm, Benign & MailWasher, to see if any are set to block or isolate attachments. All seems to be set correctly & .zm9 doesn't appear in any of the settings lists, nasty or normal.
Just thought I'd post the complete solution to what was happening.
.zm9 is the re naming of zip files by ZoneAlarm MailSafe as the above links explain.
I was unable to open the attachment & ZoneAlarm was not displaying the usual warning screen, however, double clicking the message in my inbox window showed that the attachment had access blocked by Outlook Express as well. By double clicking the attachment in this window, the ZoneAlarm Warning duly launched & I was able to open & save the file.