- Invitations: each user can invite two friends by email (sign-up works
through the link even while registration is closed); admin-editable
template, subject and sender.
- Invitation sender defaults to the system-mail From address, which the
SMTP account is allowed to send as (was postmaster@APP_DOMAIN, refused
with 553 when the two differ).
- Sign-in, sign-up and forgot-password fields show the fixed
@domain after the typed name; the registration status reports it.
- System mail gets a Date header; the invitation's plain-text part keeps
its paragraphs and line breaks.
- SMTP EHLO uses SMTP_HELO_NAME / APP_DOMAIN, not the container name.
- DNS recommendations for the mail domains.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
