jetpack_contact_form_email_headersAllow customizing the email headers. Warning: DO NOT add headers or header data from the form submission without proper escaping and validation, or you’re liable to allow abusers to use your site to send spam. Especially DO NOT take email addresses from the form data to add as CC or BCC headers without strictly validating each address against a list of allowed addresses.
jetpack_contact_form_akismet_valuesFilter the values that are sent to Akismet for the spam check.
jetpack_contact_form_in_comment_disallowed_listFilter whether a submitted contact form is in the comment disallowed list.
jetpack_delete_spam_feedbacks_limitFilter the amount of Spam feedback one can delete at once.
grunion_after_feedback_post_insertedFires after the feedback post for the contact form submission has been inserted.
grunion_after_message_sentFires an action hook right after the email(s) have been sent.
jetpack_contact_form_submit_button_classFilter the contact form submit button class attribute.
jetpack_contact_form_input_classFilters the “class” attribute of the contact form input
jetpack_daily_akismet_meta_cleanup_beforeFires right before deleting the _feedback_akismet_values post meta on $feedback_ids
jetpack_daily_akismet_meta_cleanup_afterFires right after deleting the _feedback_akismet_values post meta on $feedback_ids
Jetpack Developer Resources 