iPGMail is described as 'With governments and corporations increasingly infringing upon our privacy, we must take steps to protect our private communications and files. With OpenPGP encryption, you can secure your messages and files to ensure that only the intended recipients are able to read them' and is an app in the Security & Privacy category. There are three alternatives to iPGMail for a variety of platforms, including Mac, Linux, Online / Web-based, Windows and Android. The best alternative is GnuPG, which is both free and Open Source. Other great apps like iPGMail are OpenPGP (Free, Open Source) and S/MIME (Free, Open Source).
GnuPG allows to encrypt and sign your data and communication, features a versatile key management system as well as access modules for all kinds of public key directories. GnuPG, also known as GPG, is a command line tool with features for easy integration with other applications.
OpenPGP is the most widely used email encryption standard. It is defined by the OpenPGP Working Group of the Internet Engineering Task Force (IETF) as a Proposed Standard in RFC 4880. OpenPGP was originally derived from the .
S/MIME (Secure/Multipurpose Internet Mail Extensions) is a standard for public key encryption and signing of MIME data. S/MIME is on an IETF standards track and defined in a number of documents, most importantly RFCs 3369, 3370, 3850 and 3851.