What’s the difference between global deliverability issues and single-provider issues?

Global issues (all providers affected):

• Authentication failure (SPF, DKIM, DMARC)
• Major blocklist listing (Spamhaus)
• Domain-level reputation collapse
• Infrastructure outage
• Characteristics: Uniform decline across all providers simultaneously.

Single-provider issues:

• Provider-specific algorithm change
• Provider-specific complaint threshold exceeded
• Provider-specific trap hits
• Account-level provider issue
• Characteristics: One provider declines while others remain stable.

Diagnostic approach:

• Segment metrics by provider first
• If all affected, look for global causes
• If one affected, look for provider-specific causes

Storm affecting all ports versus one port closing. Different problems, different responses.