Shared IPs pool reputation across senders, while dedicated IPs make you solely responsible for your own.
Key points
- On a shared IP, other senders' complaints and bounces affect your IP Reputation, for better or worse [1][2].
- A dedicated IP needs consistent volume and an Email Warmup period before receivers trust it [1].
- Mailbox providers now weigh Domain Reputation heavily, so a clean domain matters on either kind of IP [3].
- Every sending IP, shared or dedicated, needs valid forward and Reverse DNS (PTR Record) records under Gmail's sender rules [3].
- Microsoft's SNDS lets owners of dedicated IPs see complaint and trap data for Outlook.com traffic [4].
How shared IPs work
Most Email Service Provider (ESP) platforms place smaller customers on pools of IP addresses that many accounts share. Because receivers see a steady, mixed stream of mail from those IPs, the pool usually has an established reputation from day one, and a new sender does not need to warm up an address on its own [1]. The trade-off is exposure. If another customer on the pool sends to a bad list, the resulting complaints or Spam Trap hits can lower the pool's standing and affect everyone on it. Reputable providers manage this by vetting customers, splitting pools by traffic quality and moving problem accounts out, but the sender has no direct control. Mailbox providers such as Gmail and Outlook host shared infrastructure of their own for ordinary users.
When a dedicated IP makes sense
A dedicated IP gives one sender full ownership of its reputation. SendGrid's documentation walks through warming up each new dedicated IP gradually, and suggests that senders reaching 250,000 messages a month use at least two dedicated IPs, one for marketing and one for transactional mail [1]. Low or irregular volume is a problem: receivers need a steady stream of mail to form a view, so a dedicated IP sending a few hundred messages a week can end up with a weaker reputation than a well-run shared pool. The M3AAWG sender best practices also stress consistent identity and volume as the basis of trust [2]. Owners of dedicated IPs can register them in Microsoft's SNDS to see Outlook.com data [4].
What this means for cold email
For one-to-one Cold Email, the question is usually moot. Messages sent from a Google Workspace or Microsoft 365 mailbox go out through the provider's own shared infrastructure, and reputation is judged mostly on the sending domain, Email Authentication and recipient behavior [3]. That makes domain hygiene, Sending Limits and a low Spam Complaint Rate more important than IP choice. PineLead sends from the mailbox you connect, so mail uses your provider's servers and your domain's records, with a daily send limit per mailbox. Dedicated IPs matter mainly for high-volume marketing or Transactional Email sent through an ESP, where volume is large and steady enough to sustain one.
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