Postfix and SPF macros: the detail that breaks delivery

While tuning an SPF record I ran into the fact that the %{i} macro is evaluated differently by some validators than by real Postfix with policyd-spf. The result: tests pass, production rejects.

Lesson: always verify SPF against the real recipient (e.g. with mail-tester), not just a syntax validator. Use macros only where they are genuinely necessary.