Fix Low IP Reputation and Restore Email Deliverability

Low IP reputation means recipient servers are rejecting your mail because the sending IP has a poor history. Unlike domain reputation, IP reputation lives with the server. Recovery is faster than domain recovery if you act on the right signals.

Bounce messages that signal IP reputation problems

Outlook and Microsoft blocks

• "The sending server’s IP address is on a block list"
• "The sending server’s IP is blocked due to poor reputation or suspicious activity"

General reputation issues

• "The sending server’s IP is blocked or blacklisted due to poor reputation or spam reports"
• "The sending server’s IP has a history of violating recipient policies"

Blacklist-related

• "The sending server’s IP is on a blocklist"
• "The sending server’s IP address is listed on one or more DNS-based blacklists"

Shared IP vs dedicated IP

Sparkforge runs a shared IP pool by default. Reputation is professionally managed across the pool, no warm-up required, suitable for most senders. Dedicated IPs are available for high-volume senders (typically 150,000+ emails/month) who want full control and built-in SNDS monitoring.

IP vs domain reputation

IP reputation: tied to the sending infrastructure, recovers quickly with the right practices, mostly affects delivery speed.

Domain reputation: tied to your domain, follows you across providers, drives long-term inbox placement.

Step 1: Identify your IP setup

1. Go to Settings → Email Services.
2. Look for the Postmaster Tools tab and the Microsoft SNDS section.
3. If SNDS data appears, you’re on a dedicated IP. If it says "IP not found in your account," you’re on the shared pool — which is the right answer for most senders.

Step 2: Fix what you control

Shared IP users

Sparkforge handles IP reputation. Focus on:

• SPF, DKIM, and DMARC verified for your sending domain
• Clean lists — segment unengaged contacts (90+ days no activity)
• Double opt-in for new subscribers
• Relevant content matched to subscriber expectations

Dedicated IP users

1. Open Settings → Email Services → Postmaster Tools → Microsoft SNDS.
2. Track complaint rate (target under 0.1%), trap hits (target 0), volume consistency, and authentication success (target above 95%).
3. Check external blacklists at MXToolbox and Spamhaus. Submit removal requests where listed.
4. If you’re ramping a new dedicated IP, warm up over 4–6 weeks starting with engaged contacts.

External tools worth checking

• Sender Score — senderscore.org
• Talos Intelligence — talosintelligence.com/reputation_center
• Google Postmaster Tools — postmaster.google.com
• MXToolbox Blacklist Check, Spamhaus, MultiRBL

Recovery timelines

Shared IP: domain auth fixes show up in 1–2 weeks; stable performance inside a month.

Dedicated IP: address blacklists in days 1–7; gradual SNDS improvement weeks 2–6; full recovery 2–4 months with steady volume.