<font color="#3300ff">UPDATE - 30 July 2008:</font> Top marks to Ironport - they got onto me very rapidly and have been extremely helpful. It now appears that this problem is a combination of an ISP who is blacklisting his own netblocks (doh!), and a slightly ambiguously-worded error response from the Ironport appliance involved. It appears at this stage that the problem is an isolated occurrence, and that there is no cause for concern. But I want to reiterate how wonderful it is to encounter a large vendor this responsive - excellent work, Ironport. ----------------------------- Original posting below ------------------------------------- It's been brought to my attention that a large company that develops anti-spam mail server appliances, Ironport (http://www.ironport.com), may have begun rejecting mail sent by Pegasus Mail because it erroneously believes Pegasus Mail is a spam generation program. [:(] [8o|] We're still investigating this and will keep you informed, but for now, if you find at any stage that you get a mail message returned to you with a 554 diagnostic that talks about your message not being accepted because of the "poor reputation of the MTA" you're using, please let us know on the forums. If anyone here knows how to get in touch with Ironport Systems (their web site is essentially purely a marketing site and has no technical value), we'd also be very grateful if you could let us know. -- David --