What’s the first step when open rates drop suddenly?

Initial response to sudden open rate drops:

Step 1: Do not panic. Avoid making multiple changes simultaneously.

Step 2: Check authentication:

SPF, DKIM, DMARC passing?

Any DNS changes recently?

Step 3: Check postmaster tools:

Gmail Postmaster reputation

SNDS for Microsoft

Step 4: Check blocklists: MXToolbox, Spamhaus lookup

Step 5: Identify scope:

All providers or specific ones?

All campaigns or specific ones?

All segments or specific ones?

Step 6: Review recent changes: What changed in the past 48-72 hours?

Systematic investigation prevents misdiagnosis.

When cargo stops arriving, first check if the port is closed, then check if the ship is damaged.