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.