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

Global versus provider-specific 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.