I18N for automatic messages (bounces)

[chibenwa]

Why?

Today TeamMail generates bounces in english. Regardless of the "locale" of the recipient.

Those bounces includes:

• Over quota
• Recipient do not exist
• Unspecified Error
• Relay denied
• Size exceeded
• Impossible to relay
• RRT error
• Virus

How?

(Ideally do not recreate the wheel and do not re-implement the wheel, ie do not re-implement Bounce)

• In Apache James define an API that given a mail provides all text part to assemble for assembling a Bounce / DSNBounce message
• Do a default, static implementation that does today behaviour (no breaking change)
• In TMail provide an implementation of this interface:
  • Use the Accept-Language header and fallback to the Content-Language header to determine user locale.
  • Use a template engine (moustache) with per-locale predefined templates
  • Use configuration to supply one message per locale
• Update tmail configuration to adopt this i18n in all deployments

Supported locale: en, fr, vn, ru, ar

Related

Position Content-Language and Accept-Language on frontend side: linagora/tmail-flutter#2215

This makes this approach compliant with: tmail, thunderbird, office365 at least, likely more.