Email Encryption
S/MIME, OpenPGP, GINA, and TLS in practice.
NewNew Outlook: S/MIME signature cannot be verified in secondary account, attachments missing
The new Outlook reports that the S/MIME signature cannot be verified in a secondary account for a shared mailbox and does not display attachments. This article explains the difference between Clear Signing and Opaque Signing, why attachments disappear from opaque-signed messages, why the new Outlook processes S/MIME only in the primary account, and what workarounds are available, including unpacking smime.p7m with PowerShell or OpenSSL.
Rebuilding Apache James Rule Sets in a Structured Way: Tools and Method
Mailet rule sets that have grown over the years contain dead paths that no one recognizes anymore. Learn how to analyze the rule set as a graph, reliably find unreachable code, and design the migration so that a single Mailet keeps the rollback path open.
Guide for DNS Administrators: MX, SPF, DKIM, DMARC, and Common Pitfalls
Anyone managing a zone will usually receive ready-made mail records and only needs to publish them. What regularly goes wrong: the 255-byte limit for DKIM, duplicate SPF records, the lookup limit, MX pointing to a CNAME, automatically appended zone suffixes, and policies nobody enforces anymore.
Testing SMTP on Linux: From the TCP Connection to Delivered Email
When an appliance stops delivering email, a manual SMTP test is more useful than any log. Learn how to check each layer using built-in tools, what different error patterns mean, and why a load balancer can distort diagnosis.
