Mailcellar: libpff source code

Mailcellar for Mac reads Outlook PST and OST files with libpff, Joachim Metz’s library, used under the GNU Lesser General Public License, version 3 or later (LGPL-3.0-or-later). This page has the exact libpff source code we ship, the script that builds it, the license texts, and how to use your own libpff with Mailcellar.

Which libpff is in which Mailcellar

Mailcellar	libpff	In the app
1.0	release 20260926, unmodified	`Mailcellar.app/Contents/Frameworks/libpff.1.dylib`

When a Mailcellar update uses a newer libpff, its source is added here, and the source for every version still offered stays here too.

Downloads

File	What it is	SHA-256
libpff-alpha-20260926.tar.gz (2.1 MB)	libpff’s release source, as published by its author	`81a8cf42e69509938bb75ca74471094d3cbd17506f3d84d0e2c1253035960c23`
libpff-alpha-20260926.tar.gz.asc	The author’s GPG signature for it (key `0ED9 020D A90D 3F6E 70BD 3945 D962 5E5D 7AD0 177E`)	`82d7faa924954f39622eef044edcfd044d66ae9c9bb1d416868583d23d98a386`
build-libpff.sh	The script we build `libpff.1.dylib` with	`6aadbd1bfaa4ed32bf08c819e01ed6391faf31ed47a89796ad519c048fa47547`
COPYING.LESSER	GNU Lesser General Public License, version 3	`e3a994d82e644b03a792a930f574002658412f62407f5fee083f2555c5f23118`
COPYING	GNU General Public License, version 3 (the LGPL builds on it)	`3972dc9744f6499f0f9b2dbf76696f2ae7ad8af9b23dde66d6af86c9dfb36986`

libpff’s own home is github.com/libyal/libpff.

How to build it

On a Mac with Xcode (for clang) and GnuPG installed, run zsh build-libpff.sh. It downloads the same tarball from libpff’s GitHub release, checks its SHA-256 and signature, and builds a universal (Apple silicon and Intel) libpff.1.dylib for macOS 14 or later with the install name @rpath/libpff.1.dylib. It works in ~/Library/Caches/ClaudeApps/Mailcellar-gate; the result is in its install/lib folder. To build from the tarball on this page instead, put it in that folder’s dl folder first.

Using your own libpff with Mailcellar

You may change libpff and use your version with Mailcellar:

Build libpff (with build-libpff.sh, or any interface-compatible version) as libpff.1.dylib with the install name @rpath/libpff.1.dylib.
Copy it over Mailcellar.app/Contents/Frameworks/libpff.1.dylib.
Re-sign the app for your own use: codesign --force --deep --sign - Mailcellar.app (ad hoc, without the hardened runtime). macOS may ask you to approve it once in System Settings › Privacy & Security.

Mailcellar’s license terms don’t forbid modifying libpff, or reverse engineering Mailcellar to debug such modifications. The same notice and steps are in the app under Help › Acknowledgements and Licenses.

A copy by email

If you’d rather get these files another way, ask through the contact page and we’ll send them.