I have been using the Blat DLL for some time. Just started using version 2.6.1. In my program, I create an HTML file containing the message as well as a text file containing the alternative text. The new version appears to keep the file open since I get an error when I try to open the file again to send another message. I do not receive the message when I close the program and start it over. It does not happen when I use version 2.5.1. I am using XP since I see that you changed the way you open files depending upon the OS, you may have missed something on closing it.
Thanks for your help on this and know that I appreciate all that you do on Blat as I do similar work on other open source/free software.