# Courier 0.46

Contents of this NEWS file:

> Overhauled Courier home page.
> Sender Policy Framework
> Older stuff

### Overhauled Courier home page

http://www.courier-mta.org has undergone a facelift. It sports improved navigation, and better organizations. Mozilla and Firefox users have an extra bonus: the leftmost button in the navigation bar is a pop-down menu that allows easy navigation between the major sections: Courier, Courier-IMAP, SqWebMail, and Maildrop. Internet Explorer does not have the required level of CSS support (no support for transparent background and absolute positions), so the popdown menu does not work with MSIE.

### Sender Policy Framework

Courier now implements the evolving SPF protocol for validating E-mail addresses. The ESMTP `HELO`, `MAIL FROM`, and the `From:` headers can be validated with SPF. There are several options that control the flexible SPF implementation. SPF support is implemented through the `bofh` configuration file.

### Older stuff

Starting with Courier 0.45, the default configuration enables metadata dot-locking. In previous version metadata dot-locking (`IMAP_USELOCKS` setting in the imapd configuration file) is disabled by default. Dot-locking was, and still is optional. When enabled, its value-added functionality is elimination of certain non-critical race conditions with concurrent access. Dot-locking is now enabled by default due to its proven record of "mostly harmless", and that it now provides added benefit with ACLs and shared folders. However, when upgrading from an earlier version, the existing configuration setting is left in place; only new installation of Courier will default to enabled dot-locking.

### Shared folders and access control lists

New to Courier 0.45 are the ACL (access control list) IMAP extension, and ACL-based virtual shared folders. Courier 0.45 implements both the existing ACL specification, RFC 2086, as well as an experimental implementation of the second draft revision of the ACL specification. Virtual shared folders is a different implementation of shared folders that supplements an older implementation in previous versions. The older, POSIX permission-based shared folders are still implemented and supported. Here's a summary of the differences between the two shared folder mechanisms:

> POSIX-based shared folders | ACL shared folders
> --- | ---
> May be used with system accounts only1 | May be used with virtual accounts only; cannot be used on systems that have end-user login shell access: bypassing ACLs and accessing the folders directly is trivial
> Access rights based on traditional POSIX filesystem permissions | Access rights based on IMAP access control lists
> Sharable folders must be set up manually, using the "maildirmake" command | A site-specific process must be installed to compile an index of all virtual mailboxes; afterwords, individual users may create and manage shared folders themselves

> > 1 This is because access rights are governed by filesystem permissions. POSIX shared folders may also be used with virtual accounts, but it will not be possible to grant read-only access to shared folders, and everyone will be able to delete messages from shared folders (instead of only the creator of each message)

After installation, read the "maildiracl" manual page for a brief overview of access control lists.

Read "maildir/README.sharedfolders.html" for information on configuring virtual shared folders