Since version 3.5 gpg4o is able to point out that a newer version of GnuPG exists to provide our users security relevant updates of the encryption component. Users of gpg4o may get a message at the startup of Outlook that there is an older version of GnuPG available and asks if it should “update” to this version.
After the release of GnuPG 1.4.21 we found out that gpg4o does not work well with some outputs of GnuPG. This is especially the case when analysing unencrypted emails and attachments and occurs often (but not only) when analysing Microsoft Office documents. The effect of this behaviour is that the user is prompted by a dialog to enter his passphrase or the email and its attachments are not displayed correctly.
To prevent further problems we decided to recommend the installation of the previous GnuPG v1.4.20 instead of the latest v1.4.21. At the moment we are working hard on the upcoming gpg4o v5.1 which will be able to work better with 1.4.21 and after its release we will recommend to install GnuPG 1.4.21 again.