https://github.com/mikel/mail
Ruby
A Really Ruby Mail Library
Mail::Part#add_content_id
Creates a new empty Content-ID field and inserts it in the correct order into the Header. The ContentIdField object will automatically generate a unique content ID if you try and encode it or output it to_s without specifying a content id. It will preserve the content ID you specify if you do.
Edit
git clone [email protected]:mikel/mail.git
cd mail
open lib/mail/part.rb
Contribute
# Make a new branchgit checkout -b -your-name--update-docs-Mail--Part-add_content_id-for-pr
# Commit to gitgit add lib/mail/part.rbgit commit -m "better docs for Mail::Part#add_content_id"
# Open pull requestgem install hub # on a mac you can `brew install hub`
hub fork
git push <your name> -your-name--update-docs-Mail--Part-add_content_id-for-pr
hub pull-request
# Celebrate!