Shared vs dedicated sending IPs
A shared IP address carries mail from many customers of an email service provider, so its reputation is the sum of everyone's sending. A dedicated IP carries only your mail, so its reputation reflects only your practices. A dedicated IP pays off when you send large volumes on a steady, predictable schedule; for low or irregular volume, a well-run shared pool usually delivers better. Either way, mailbox providers also judge your domain, so a new IP does not give you a fresh start.
How reputation works on each
Shared IPs
Google's email sender guidelines put it plainly: what any sender does on a shared IP affects the reputation of every sender on it. Twilio SendGrid's dedicated IP documentation adds that shared IPs can change without notice, and that your mail can be throttled or blocked when others on the same IP break inbox provider standards. Amazon SES says that on its shared addresses, it controls the sender reputation and manages the outbound traffic (Dedicated IP addresses for Amazon SES).
Sharing has real benefits too. M3AAWG's Sender Best Common Practices (section 2.6) explains that combining many senders keeps the overall volume steady, which IP reputation depends on, and that one sender's mistake is diluted across the pool. The flip side, in the same section: one sender with poor list practices can damage the environment for everyone, so providers should vet who they put on shared IPs.
Dedicated IPs
On a dedicated IP, your account is the only one sending, so the reputation follows from your own practices (SES and SendGrid say this in the pages above). That cuts both ways. A clean program is no longer held back by a neighbor, and a sloppy one has nobody to dilute it.
Your domain is judged either way
The IP is only half the picture. Google tracks volume, feedback and limits per domain and per IP, and says user spam reports lower a domain's reputation over time (sender guidelines). Yahoo's sender best practices say each IP and each DKIM domain has its own reputation. So moving a domain with complaint problems to a dedicated IP brings the domain's history along. M3AAWG (section 2.6) makes the positive version of the same point: signing with DKIM on your own domain or subdomain lets receivers tell senders on a shared IP apart, and lets you carry a good reputation with you if you move. More on how both kinds of reputation are built in sender reputation.
Shared and dedicated compared
| Item | Shared IP | Dedicated IP |
|---|---|---|
| Whose behavior counts | Everyone on the IP or pool | Yours alone |
| Warm-up | Not needed for the IP | Needed before full volume |
| Volume needed | Works at low volume | Needs steady, sizable volume |
| Irregular sending | Absorbed by the pool | Poor fit (except SES managed IPs) |
| Known, fixed address | No, it can change | Yes (standard dedicated IPs) |
| Separate streams by IP | No | Yes, with IP pools |
| Cost | Included in the plan | Extra fee |
The rows follow the comparison table in the SES dedicated IP guide; SES's managed dedicated IPs are the exception noted for irregular sending.
When a dedicated IP makes sense
Volume and consistency
Steady volume matters more than high volume. M3AAWG (section 2.6) says consistency of volume, high or low, plays an integral part in IP reputation, especially at free webmail and other large mailbox providers. Amazon SES recommends shared IPs unless you plan to send large volumes on a regular, predictable basis, and notes that most mailbox providers only track an IP's reputation once they receive a significant amount of mail from it.
Email service providers publish their own guidance. These are each provider's numbers for its own platform, not rules set by Gmail, Yahoo or Microsoft:
| Provider | What it says |
|---|---|
| Amazon SES | Send several hundred messages within 24 hours, at least once a month, to each mailbox provider you want a reputation with; after warm-up, around 1,000 a day per provider and IP. |
| Twilio SendGrid | At 250,000 messages a month, use at least two dedicated IPs, one for marketing and one for transactional mail; plan one IP per three to four million messages a day. |
| Mailgun | Above 50,000 messages a week, isolate your reputation on a dedicated IP; under 5,000 a day, a shared IP may be the right choice. |
| Postmark | At least 300,000 messages a month for a dedicated IP, and a second IP at 100,000 or more a day. |
Other good reasons
- Separating mail streams. With dedicated IPs you can put marketing and transactional mail in separate pools (SES calls them dedicated IP pools). See transactional vs marketing email.
- A known address. Standard dedicated IPs in SES are static. SES notes they can suit even small volumes sent to a defined group of recipients whose servers accept mail from a list of specific IPs.
- Your own reverse DNS. M3AAWG (section 2.6) recommends that each dedicated IP's PTR name identify the customer, not the provider. See reverse DNS for mail servers.
When shared is the better choice
Stay on shared IPs if your volume is low, seasonal or bursty, or if you cannot commit to the monitoring a dedicated IP needs. Postmark says a clean shared pool serves most of its senders well, and M3AAWG notes that shared environments are what make sending affordable for very small businesses.
Warm-up
A shared IP is already warm. SendGrid says customers on its shared pools need no warm-up strategy (Warming up an IP address). A new domain or subdomain is still unknown, though, and M3AAWG (section 2.5) recommends warming a new subdomain even when the parent domain has a good reputation.
A dedicated IP starts with no history. SES says building a positive reputation takes around two weeks at some mailbox providers and up to six weeks at others (Warming up dedicated IP addresses); Postmark expects three to six weeks with its managed warm-up. Warm-up is not one-time: SendGrid advises warming again after more than 30 days without sending, and Postmark requires it again after four weeks below 20,000 messages a week. The method is the same as for any new sender, covered step by step in email warm-up.
Managed and automatic warm-up
Several providers will pace the ramp for you:
- Amazon SES, standard dedicated IPs: automatic warm-up is on by default. SES splits your mail between the new IPs and shared (or already warm) IPs and raises the share over 45 days, on a schedule that does not depend on your volume.
- Amazon SES, managed dedicated IPs: SES allocates the IPs, warms them for each mailbox provider separately based on your actual sending, and scales the pool up or down with demand. SES positions this option for less predictable sending patterns.
- Twilio SendGrid: automated warm-up caps each new IP's hourly volume and sends the overflow through another IP, so you need at least one IP that is already warm.
- Postmark: sets a daily limit, raises it as reputation builds, and routes the rest through its shared pool.
Automation controls the pace, not the quality. SendGrid says itself that a gradual warm-up does not guarantee a good reputation. Start with engaged, verified recipients and watch deferrals such as 421 4.7.28, Gmail's rate-limit deferral.
Costs
Shared IPs are part of the base price at most providers. SES charges a monthly fee per leased standard dedicated IP, and a monthly fee plus a per-message charge for managed dedicated IPs; SendGrid includes one dedicated IP in some plans. The larger cost is often time: with a dedicated IP, monitoring Google Postmaster Tools, Microsoft SNDS and blocklists becomes your job, not the provider's.
Before you switch
- Authenticate the mail with SPF, DKIM and DMARC on your own domain, checked with the DKIM checker and DMARC checker.
- Clean the list first. Bounces weigh most on an IP with no history. Run your list through bulk email verification and drop every result with the action
remove. - Set up monitoring in Google Postmaster Tools and Microsoft SNDS, and know how to check blocklists.
Questions
Will a dedicated IP fix my deliverability?
Only if a neighbor on a shared IP was the cause. Complaints, bounces and unwanted mail follow you to any IP, and your domain's reputation moves with you.
Does a new dedicated IP reset a bad reputation?
The IP starts without history, but your domain keeps its record at Gmail and Yahoo, which both track domain reputation separately from the IP.
Can I use shared and dedicated IPs together?
Yes, at some providers. SES and SendGrid both send overflow through shared or already warm IPs during warm-up, and Postmark routes it through its shared pool.
Try it
Clean the list before you warm up a new IP with bulk email verification, or spot-check a few addresses with the free email checker.
Related
- Glossary: sender reputation and bounce rate.
- Bounce code 421 4.7.0: temporary policy deferrals, often reputation-related.
- List cleaning: what to remove before a warm-up.
Related guides
- Email warm-up for new IPs and domains
- Sender reputation explained
- Transactional vs marketing email
- Reverse DNS (PTR records) for mail servers
- How to use Google Postmaster Tools
- All guides
Sources
- Google: Email sender guidelines: shared IP reputation, per-domain and per-IP tracking, separate IPs per message type.
- Yahoo: Sender best practices: reputation per IP and per DKIM domain.
- M3AAWG: Sender Best Common Practices, version 4.0: section 2.6 on shared and dedicated environments, section 2.5 on domain warming.
- Amazon SES: Dedicated IP addresses for Amazon SES: the comparison of shared, standard and managed IPs, volume guidance, costs.
- Amazon SES: Warming up dedicated IP addresses (standard): warm-up duration, automatic 45-day warm-up, daily volume after warm-up.
- Twilio SendGrid: Dedicated IP addresses: shared pools, volume guidance, automated warm-up overflow.
- Twilio SendGrid: Warming up an IP address: no warm-up on shared pools, re-warming after 30 days.
- Mailgun: IP addresses and sending volume: weekly and daily volume guidance.
- Postmark: Dedicated IPs: minimum volume, managed warm-up, re-warming.
How we wrote this: drafted by the email-validation.org team with the help of AI writing tools, from our product documentation and the sources linked in the text.