I noticed two translation problems with the Email templates in the Administration → Customize → Email templates section.
1. Titles of email templates are not translated:
Clarification: The title of an email template is not its subject.

This is because the AdminEmailTemplateSerializer only “titleizes” the keys of the email templates (e.g. system_messages.bulk_invite_failed becomes Bulk Invite Failed) here:
2. Four email templates are missing in I18n:
- 
system_messages.email_reject_destination
- 
system_messages.email_reject_post_error
- 
system_messages.email_reject_post_error_specified
- 
system_messages.email_reject_trust_level
Update: Looks like artifacts, as not referenced anywhere (added links to GitHub search).
