File sharing is an important aspect of modern (business) communication. Sharing via email is often constrained by file size limits. To overcome such limitations, users often turn to external file transfer services like Dropbox’s DocSend, WeTransfer, or SURFfilesender (in the academic world). File encryption typically requires choosing a password that must be exchanged out-of-band with recipients. As an alternative, Identity-Based Encryption (IBE) provides a more seamless solution, leveraging recipients’ identities to eliminate the need for password sharing. This paper introduces PostGuard, a practical implementation of IBE for securely sharing large files. PostGuard integrates an identity wallet for authentication. The paper details PostGuard’s cryptographic design and protocol, analyzes its confidentiality guarantees via attack trees, and proposes countermeasures for the potential attacks. Furthermore, PostGuard is compared with other file transfer services, with respect to general and security-related criteria. The scores of the different tools show considerable variation. This study bridges the gap between theoretical IBE research and practical secure file transfer implementations, contributing to the broader adoption of IBE-based solutions.