Found a corner case bug, now that I know it's characteristics I can avoid it but I thought I'd bring it to your attention. Using Mozilla's Thunderbird mail client if you forward a message to the postie mailbox and that message has more than 1 image attached and you have multiple #imgx# tags in the content body it will only substitute the first #imgx# all the other ones get skipped ($attachments only has 1 member when it gets to "filter_ReplaceImagePlaceHolders" causing the loop to only execute once) . Outlook and Apple Mail all seem to work fine it's only Thunderbird that has this problem and it only happens on forwarded mails. Newly created emails with multiple images and multiple #imgx# tags work fine. I was able to chase it down to the function "GetContent" were it got past my ability to follow because it looks like Thunderbird is doing something with the separater content-xx tags in the raw email.
The pertinent debug output is "GetContent: secondary lookup failed, checking configured extensions"
Good luck, Great plug in, Thank You.