Editing Maildir (section)

== File-system compatibility issues ==

The Maildir standard can only be implemented on systems that accept colons in filenames. <ref>{{Cite web |title=mailbox — Manipulate mailboxes in various formats |url=https://docs.python.org/3/library/mailbox.html |access-date=2023-06-19 |website=Python documentation}}</ref>

Systems that don't allow colons in filenames (this includes [[Microsoft Windows]] and some configurations of [[Novell Storage Services]]) can use a non-standard alternative separator, such as ";" or "-". It is often trivial to patch [[free and open-source software]] to use a different separator.<ref name="mutt-colons"/>

As there is currently no agreement on what character this alternative separator should be, there can be interoperability difficulties between different Maildir-supporting programs on these systems. However, not all Maildir-related software needs to know what the separator character is, because not all Maildir-related software needs to be able to read or modify the flags of a message ("read", "replied to" etc.); software that merely delivers to a Maildir or archives old messages from it based only on date, should work no matter what separator is in use. If only the [[email client|MUA]] needs to read or modify message flags, and only one MUA is used, then non-standard alternative separators may be used without interoperability problems.