Migrating procmail rules to Sieve with a real parser
Summary
Manuel Schmitt replaces an unreliable procmail-to-Sieve converter with his own parser with a deliberately limited scope. The earlier converter was partly based on free scripts, including earlier work from Dovecot. The new converter was rewritten completely in-house.
Ideas
- A parser understands rule structures more reliably than a series of simple text replacements.
- Rare nested procmail blocks deliberately remain outside the supported scope.
- A migration may leave out expert cases if it clearly states these limits.
Insights
- Good converters gain trust through precise limits rather than pretended completeness.
- Old mail filters are executable operational logic and deserve tests like other source code.
Facts
- Nested blocks with curly braces are not translated automatically.
Recommendations
- Test converted rules with a representative corpus of messages.
- Keep the procmail rules and document every manual Sieve adjustment.
References
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