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From Expired Certificates to Identity Mismatches: How Well Do Email Clients Communicate S/MIME Issues?

Year: 2026

Type: conference-paper

Abstract: This research explores how modern email clients handle security and technical issues associated with S/MIME encrypted and signed emails. By testing 13 widely used clients across multiple platforms, it examines how well they detect common issues - such as expired or revoked certificates and mismatched sender identities - and how clearly these problems are communicated to users. The results show noticeable differences in detection accuracy: while some clients consistently performed well, others - particularly Android-only apps and mobile versions - proved less reliable. Warning clarity also varied, with some clients providing misleading information. Overall, the findings show that even though S/MIME has been available for many years, many email clients still struggle to properly handle and communicate related security issues.

Source: Repository KITopen (Karlsruhe Institute of Technology)

DOI: 10.5445/ir/1000196778

Authors: Gemov, Mario, Ballreich, Fabian Lucas, Volkamer, Melanie

Language: English

Topic: User Authentication and Security Systems

Subfield: Information Systems

Field: Computer Science

Domain: Physical Sciences

Open Access status: green

OpenAlex ID: W7208770072

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