When your mail arrives, the receiving server sees an IP address before it sees your domain. If that address has sent spam, mail from it is treated with suspicion, whoever is sending now.
Shared and dedicated
| Shared IP | Dedicated IP | |
|---|---|---|
| Who sends from it | Many Amazon SES customers | Only you |
| Whose behaviour counts | Everyone’s | Yours |
| Warm-up needed | Not by you | Yes. See IP warm-up |
| Cost | Included | Extra monthly cost, see dedicated IP |
| Best for | Most senders, especially smaller or irregular ones | High, steady volume |
On shared pools your mail is pooled with other senders, which is one reason AWS holds every account to its bounce and complaint limits.
What affects it
The same things that affect sender reputation: bounces, complaints, spam traps, volume that jumps around and mail people do not want. With a dedicated IP you carry all of it. A single bad campaign can cost the IP its standing for weeks.
Checking an IP
Look the address up on the major blocklists. Check what the provider reports back: Google Postmaster Tools shows how Gmail sees your domain, and other providers have similar dashboards.
Domain matters more now
Mailbox providers have shifted weight toward domain reputation, because IP addresses are easy to change and domains are not. A clean IP with a poorly authenticated or poorly regarded domain still struggles.
Common questions
Do I need a dedicated IP on Amazon SES?
Usually not. Shared IPs are managed by AWS and work well for most senders. A dedicated IP makes sense when your volume is high and steady and you want your reputation to depend only on you.
Does IP reputation matter if I use a shared IP?
Less. AWS manages the pools, so you cannot fix it yourself. Your domain reputation and authentication matter more.