Updated: 28 September 2026 · Applies to: Self-managed dedicated servers that send email (Postfix)

A common reason to run a dedicated server with several IP addresses is to send email yourself: application mail, order confirmations, newsletters or a mail system for your own customers. Sending mail from your own server gives you control and a predictable cost, and it also makes you responsible for the things a mail service normally handles: authentication, reputation, bounces and unsubscribes. This overview lists what a healthy setup contains and points to a guide for each part.

What Ucartz requires from you

Ucartz's Acceptable Use Policy and terms state the rules for mail from servers you run. In short: bulk or marketing mail needs consent capture, bounce processing and unsubscribe links; SPF and DKIM must be valid (DMARC is recommended); reverse DNS (PTR) must be correct for every server that sends mail; and Ucartz may pause or restrict sending for high bounce rates, complaints or abuse reports. Read the Acceptable Use Policy before you start. The guides below follow these rules.

The checklist

  1. Clean IP addresses and a plan. Choose how many addresses you need (How many IP addresses do you need for your dedicated server?) and check each one against public blocklists (How to check whether a new IP address is on a blocklist before you use it?).
  2. Working network. Configure the addresses (How to add additional IPv4 addresses on Ubuntu with netplan? or How to add additional IPv4 addresses on AlmaLinux or Rocky Linux with nmcli?), test them (How to test that every additional IP address works on your server?) and check that outgoing port 25 works (How to check that outgoing port 25 works from your dedicated server?); the SMTP ports are enabled on all Ucartz servers.
  3. Reverse DNS for every sending address, with a matching A record (How to set reverse DNS (PTR) for many IP addresses and check forward-confirmed rDNS?).
  4. A mail server (MTA). Install and configure Postfix (How to install and configure Postfix for sending on Ubuntu?).
  5. Authentication. SPF (How to write an SPF record for a server with several IP addresses?), DKIM (How to set up DKIM signing with OpenDKIM and Postfix for several domains?) and DMARC (How to publish DMARC for your sending domains and tighten the policy safely?).
  6. Control which address sends what. Make Postfix send from a chosen address with a matching HELO name (How to make Postfix send from a specific IP address with a matching HELO name?) and give each domain or customer its own address (How to give each domain or customer its own sending IP address in Postfix?).
  7. Unsubscribe and list handling. Add unsubscribe links and headers (How to add a working unsubscribe link and one-click unsubscribe headers to your emails?) and process bounces and complaints (How to process bounces and spam complaints and keep a suppression list?).
  8. Automate what can be automated safely: stream assignments, warm-up schedules, health checks and automatic pausing (How to automate multi-IP mail management safely: assignments, warm-up schedules and automatic pausing).
  9. Warm up new addresses slowly (How to warm up a new sending IP address step by step?) and set sensible per-provider limits (How to set delivery rate limits per provider in Postfix and handle deferrals?).
  10. Know what the big mailbox providers expect (Gmail, Yahoo and Microsoft requirements for bulk senders: a checklist) and test your setup (How to test authentication and deliverability of your outgoing email?).
  11. Protect the server from misuse (How to protect your mail-sending server from misuse?) and monitor it (How to monitor your sending IP addresses automatically with a script?).
  12. Know what to do when something goes wrong: reading logs (How to read Postfix logs and understand common SMTP error codes?) and blocklist listings (What to do when your IP address is on a blocklist or your mail is rejected?).

What makes mail arrive

  • Recipients who asked for your mail. Mailbox providers measure how many recipients mark your mail as spam. Gmail asks senders to keep the spam rate reported in Postmaster Tools below 0.3%.
  • Consistent identity. The same domain and the same IP address for the same kind of mail, with matching names in DNS.
  • Gradual growth in volume for a new address.
  • Clean lists: remove hard bounces and inactive addresses.

Should I run my own or use a paid service?

Both are valid. See Dedicated server with extra IP addresses or paid sending credits: how to compare the cost for how to compare the cost, and note that your own server adds the work of operating it. Ucartz engineers can set it up and look after it for you.

Frequently asked questions

How many emails can I send per hour?
The terms set hourly limits for shared hosting, reseller, VPS and cloud plans and list no hourly cap for dedicated servers. The real limits come from the receiving mail providers and your reputation, so grow gradually.

Does the server have port 25 open?
Yes. The SMTP ports are enabled on all Ucartz servers and nothing is blocked by default. Test it with How to check that outgoing port 25 works from your dedicated server?; if a test fails, check your own firewall first.

Need a dedicated server, more IP addresses, or a hand with the setup?

Prefer a hand with the setup? Our engineers can do it for you: Hire an Expert, or use our on-demand server management.

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