The original regression only exercised a from_address match with all three
identity fields set to the same value, so it couldn't distinguish whether
_self_addresses actually picks up smtp_username and imap_username or just
collapses on from_address. Add a parametrized test covering:
- smtp_username-only match (from_address empty, imap_username different) —
simulates SMTP relays that rewrite outbound From to the login identity.
- imap_username-only match — simulates mailbox-identity setups.
- Case-insensitive match — inbound From arriving upper-cased must still hit.
No production code changes.
Made-with: Cursor