I can't get headers.dll to work since upgrading either; it shows in Extensions Manager but there's no headers in the emails.

Another workaround is to create your custom headers in the Special tab when sending emails.

These will be retained  in the recently-used list, so you have to enter them only once, then just recall them.

You could enter the headers directly into \Pmail\MAIL\<username>\WINPMFUH.PM,

and you could also backup this file - very useful if the custom headers get lost.

There's one major weakness - its not a sticky setting so you have to remember to invoke the Special tab each time.

However I suppose you have to remember to run 4.63 for your newsletters anyway; using stored custom headers seems better.

I have used Gerard Thomas' headers extension since 2007.

It stopped working when I upgraded Pegasus (windows) from 4.63 to 4.70.

There is a previous instance here:

 http://community.pmail.com/forums/thread/30971.aspx

The thread does not contain a solution, if in fact there was one, however you can ask the OP directly as to whether he overcame the problem.  

Thanks,

I had seen that post, and, interestingly, headers was working for me  in 4.62 and 4.63; only failing in 4.70.

The extension does get loaded and there are no errors in the log.  It seems that it  just does not trigger.

This is a major problem for me because without the headers gmail is blocking all of my neighborhood association e-mails.

Never did get it working.  I have had to create a VM where I keep a 4.63 version of PMail running that I use for the newsletters.

Did you try to contact Philippe Chartier directly?  He still shows up as a Beta Member and Moderator, so I assume he is still with us.