220

SMTP Code 220: Service Ready

Success Low severity Success RFC 5321
What it means

SMTP Code 220 means “Service Ready.” The receiving mail server is ready to accept your connection. This is the standard SMTP greeting message sent when a server is available and willing to begin the mail transaction.

At a glance
Code220
Bounce typeNot a bounce
SeverityLow
CategorySuccess
What to doNone; the delivery step succeeded
StandardRFC 5321
What it looks like in your mail logs 
220 mx.google.com ESMTP d75a77b69052e-46c1c0a2f9bsi.123 - gsmtp

What does 220 mean?

SMTP code 220 is the initial greeting response from a receiving mail server. When your sending server connects to a recipient's mail server on port 25 (or 587 for submission), the receiving server responds with 220 to indicate it is ready to begin the SMTP conversation. This is not a bounce code but a normal part of every successful email delivery.

The 220 response typically includes the server's hostname and sometimes its software version. For example: "220 mx.google.com ESMTP ready". If you are not receiving a 220 response when connecting to a mail server, it usually indicates a network-level issue such as a firewall blocking port 25, DNS resolution failures, or the remote server being down.

How 220 plays out

Your server connects and sends a command
The recipient responds 220: the step succeeded
The SMTP conversation continues toward delivery

Common causes of 220

  • Normal SMTP connection initiation - the server is ready
  • Server successfully resolved via MX record lookup
  • TCP connection on port 25 or 587 established successfully

How to fix 220

  • No fix needed - this is a success response
  • If you are NOT receiving 220, check that port 25 is not blocked by your firewall or ISP
  • Verify MX records point to valid, reachable mail servers using an MX Lookup tool

Frequently asked questions

What does SMTP 220 mean?
SMTP 220 means "Service Ready": the mail server is prepared to begin the SMTP conversation. It is the initial greeting your email client receives when connecting to an SMTP server, indicating the server is online and ready to accept commands. After receiving a 220 response, your client should send the EHLO or HELO command to begin the session. This is a positive status code, not an error.
Is SMTP 220 an error?
No, SMTP 220 is not an error. It is a success response code confirming the mail server is ready to proceed. All SMTP codes beginning with "2" indicate successful or positive outcomes. Some email clients may mistakenly log 220 as an error due to software bugs, but no fix is needed; the server is functioning normally.
What should happen after an SMTP 220 response?
After receiving a 220 response, the sending mail client should issue an EHLO (or HELO) command to identify itself and start the SMTP session. The server will then reply with its supported features and capabilities, allowing the client to proceed with authentication and message transmission. If nothing happens after the 220 greeting, check your client configuration or network connectivity.

Related bounce codes

221 Closing Connection 250 Requested Action Completed 421 Service Not Available - Try Again Later

Sources & further reading

RFC 5321 · The standard that defines this reply code RFC 5321 section 4.2 · Reply code 220 (Service ready) in the SMTP reply code list
Reviewed by Jennifer Jackson, Email Deliverability Analyst · June 2026 ← All bounce codes