tell application "Yojimbo"
set bookmarkName to "My Example Bookmark"
set bookmarkURL to "http://www.example.com/"
set bookmarkComments to "your comments go here"
set newItem to make new bookmark item with properties {name:bookmarkName, location:bookmarkURL, comments:bookmarkComments}
add tags {"a tag", "another tag", "important tag"} to newItem
end tell
A quick search for exporting mails found https://veritrope.com/code/export-apple-mail-messages-and-notes-to-text-files/. Adapting these two should allow you to export mails to Yojimbo. Feel free to post follow.up questions, and I'll try to help you get going.
Ulf