I also use some article plugins so i did some testing with the joomgallery and jdownloads tag
This is the article i want to show in a mail
it contains a clickable image from joomgallery and a link to jdownloads file.
This is how it show in acy 5
Image and image link are good
jdownloads tag is not processed
This is how it show in acy 7
Image is good
image link and jdownloads tags are not processed
The not working image link from joomgallery is currently my showstopper to move from acy5 to acy 7. Jdownloads links are not used that often. It seems to me if the article is first processed by the onContentPrepare from joomla (which will call the content plugins which replaces the tags with html code) and then placed in the mail all article plugins can be used.