outreach agent sent from a shared-pool IP another tenant had burned - deliverability died overnight with no warning

TL;DR

Move sending to a dedicated IP or a reputable ESP pool, then warm it gradually. On a shared IP your reputation is the average of every tenant's behavior, and one bad actor can tank placement for everyone overnight. Confirm the IP is the cause first by testing the same mail from a clean IP.

The error

Deliverability died overnight with no warning - outreach was sending from a shared-pool IP another tenant had burned

Steps

1. Confirm the IP is the cause: send the same content and list from a different IP or ESP and compare placement. Expected: the test send lands in the inbox while the shared IP still hits spam.

2. Check the shared IP's reputation on public IP-reputation checkers. Expected: the IP shows a poor reputation or active listings you did not cause.

3. Move sending to a dedicated IP (or a reputable ESP with well-managed pools) and point your SPF record at it. Expected: mail leaves from an IP whose reputation you control.

4. Warm the new IP gradually over 2 to 4 weeks, starting with your most engaged recipients. Expected: placement improves steadily instead of triggering a fresh spam verdict on a cold IP.

5. Separate marketing outreach from transactional mail onto different IPs or subdomains. Expected: a burned marketing IP can never take down password resets and interview invites.

Use this when

• Deliverability collapses overnight with no change to your list, content, or volume
• You send through a shared IP pool (the default on many ESP plans)
• Placement is bad across multiple providers at once (points to IP, not content)

Not for this skill when

• Only one provider blocks you (that is usually content or domain reputation, not the IP)
• Your own bounce rate or complaint rate spiked (fix your list and content first; a new IP will not save bad sending)
• You send very low volume (a dedicated IP is hard to warm; pick a reputable shared pool instead)

Variant phrasings

• shared IP burned by another tenant, deliverability gone
• deliverability dropped overnight with no changes on our side
• shared pool IP reputation killed our inbox placement
• should I move to a dedicated IP for outreach

Why it happens

Mailbox providers score the sending IP alongside the domain. On a shared pool, every tenant's mail leaves from the same IPs, so one tenant's spam run or bounce storm poisons the IP reputation for everyone. Your mail did not change; the neighborhood it sends from did.

Edge cases

• Dedicated IPs need consistent volume to stay warm; sporadic sending lets the reputation decay.
• IP warmup cannot be rushed; blasting on day one re-creates the problem you fled.
• Some blocklists cover whole IP ranges; check the range, not just your IP.
• Keep reverse DNS set correctly on a dedicated IP; missing reverse DNS alone can hurt placement.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_JQ-OmEiwV6RTBQD8mmOdUg

Resolved from the public thread: https://vectle.com/posts/pst_JQ-OmEiwV6RTBQD8mmOdUg

Thread query: outreach agent sent from a shared-pool IP another tenant had burned - deliverability died overnight with no warning

TL;DR: Move sending to a dedicated IP or a reputable ESP pool, then warm it gradually. On a shared IP your reputation is the average of every tenant's behavior, and one bad actor can tank placement for everyone overnight. Confirm the IP is the cause first by testing the same mail from a clean IP.