By not advertising SMTPUTF8 support at the start, senders may opt to transmit recipient internationalized domain names in IDNA form instead, which will be deliverable.
Incoming mail with internationalized domains was probably working prior to our move to Ubuntu 18.04 when postfix's SMTPUTF8 support became enabled by default.
The previous commit is retained because Mail-in-a-Box users might prefer to keep SMTPUTF8 on for outbound mail, if they are not using internationalized domains for email, in which case the previous commit fixes the 'relay access denied' error even if the emails aren't deliverable.
v0.50 (September 25, 2020)
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Setup:
* When upgrading from versions before v0.40, setup will now warn that ownCloud/Nextcloud data cannot be migrated rather than failing the installation.
Mail:
* An MTA-STS policy for incoming mail is now published (in DNS and over HTTPS) when the primary hostname and email address domain both have a signed TLS certificate installed, allowing senders to know that an encrypted connection should be enforced.
* The per-IP connection limit to the IMAP server has been doubled to allow more devices to connect at once, especially with multiple users behind a NAT.
DNS:
* autoconfig and autodiscover subdomains and CalDAV/CardDAV SRV records are no longer generated for domains that don't have user accounts since they are unnecessary.
* IPv6 addresses can now be specified for secondary DNS nameservers in the control panel.
TLS:
* TLS certificates are now provisioned in groups by parent domain to limit easy domain enumeration and make provisioning more resilient to errors for particular domains.
Control Panel:
* The control panel API is now fully documented at https://mailinabox.email/api-docs.html.
* User passwords can now have spaces.
* Status checks for automatic subdomains have been moved into the section for the parent domain.
* Typo fixed.
Web:
* The default web page served on fresh installations now adds the `noindex` meta tag.
* The HSTS header is revised to also be sent on non-success responses.
