smtp error 550

SMTP Error 550


SMTP Error 550

The SMTP error code 550 means that your requested SMTP action was not completed. Most common reason for getting this error are either:

  • recipient SMTP server is not accepting the connections from the sender
  • or the recipient of the email could not be reached because the mailbox is not found
  • or the SMTP connection is just getting rejected because of some firewall policy.

Common Error

Requested action not taken: mailbox unavailable (e.g., mailbox
not found, no access, or command rejected for policy reasons
List of SMTP 550 error codes with its possible solutions:

SMTP Error 550 “Relay Denied”

The SMTP error code 550 “Relay Denied” means that the SMTP server to which you’re trying to connect is not able to recognize you as a valid sender.
The most common reasons for 500 “Relay Denied” error is a failure to authenticate with the SMTP server. Few other reasons are:
  • Misconfiguration with the Email Client: There might be a possibility that the email client (e.g. Thunderbird, Outlook) which you’re using to connect to SMTP server is not setup correctly.
  • Incorrect SMTP Authentication Method: You have not entered the correct SMTP username or password or your email client is not configured to use the correct authentication protocol for sending emails like SMTP-AUTH. Many email clients have a autodetect or autodiscover feature to configure SMTP. If you’re using any of the popular SMTP service provider, then on the click on autofect, the rest of the configuration will be autodetected and pre-filled. Else you might have to choose the auth method manually from the list of available methods like None, Plaintext password, Encrypted password, Kerberos/GSSAPI, NTLM.
  • Incorrect SMTP Port: Port 25 is the standard SMTP port for all outgoing email communications. However there can be cases, where the SMTP providers you are using is accepting SMTP connections of some other ports too. So, try checking other popular ports like 587, 465, 2525. Also, make sure you don’t have a firewall blocking the port which you’re trying to use.
  • Incorrect SSL Method used: While doing the SMTP setup in your email client, you might have selected a SSL method to connect. By default most of the email clients have an option of “autodetect” or “autodiscover”, which by default pings the SMTP server and sets the value of SSL. But, sometimes it doesn’t works properly so you have to try selecting the appropriate SSL method from the list of available methods like None, STARTTLS or SSL/TLS. If you’re not sure, what SSL method the SMTP server is using, then you have to try hitting each method and checks which works.
  • IP Address Whitelisting: If you’re able to connect to SMTP server from one location or computer but not from another location then this might be because the SMTP server is configured to only authorise connections from a particular or a range of IP address. This issue is most commonly observed while you trying to access your corporate mailbox from your home IP address.

550-5.1.1 The email account that you tried to reach does not exist

This error usually occurs when you have done typos while mentioning the recipient’s email address. e.g. instead of typing [email protected] , you might have written [email protected]
Few popular 550-5.1.1 error messages among different service providers:
550-5.1.1 The email account that you tried to reach does not exist. Please try
550-5.1.1 double-checking the recipient's email address for typos or
550-5.1.1 unnecessary spaces. Learn more at
550 5.1.1 w41si3198459wfd.71
550 5.1.1 The email account that you tried to reach does not exist. Please try double-checking the recipient's email address for typos or unnecessary spaces. Learn more at mail/?p=NoSuchUser  u5sor6229229vkf.289 - gsmtp
The response from the remote server was:
550 5.1.1 [email protected] Recipient not found.
This error usually occurs when you have done typos while mentioning the recipient’s email address.
Few other list of popular SMTP 550 errors:
  • 550 5.7.1: Service unavailable: client[###] blocked using ###(Exchange Server)
  • 550 5.7.1: Message rejected as spam by Content Filtering(Exchange Server)
  • 550 Invalid recipient
  • 550 User account is unavailable
  • 550 This message was classified as SPAM and may not be delivered
  • 550 High probability of spam(Gmail)
  • 550 5 2 1 mail from refused spam site
  • 550 Message contained unsafe content
  • SMTP Error 5.5.0
  • 550 – Requested actions not taken as the mailbox is unavailable.
  • 550 Address rejected
  • 550 No such user here
  • 550 Not our Customer
  • 550 Account not available
  • Remote host said: 550 – [email protected], this MYDOMAIN.COM
  • Remote host said: 550-Verification failed for [email protected]
  • 550-Previous (cached) callout verification failure
  • 550 Sender verify failed Giving up on
  • Response: 550 Cyberoam Anti Spam Engine has identified this email as a spam. Refid:str=0001.0A0B0206.4BA7422C.01F5,ss=1,vtr=str,vl=0,pt =
  • 550-Verification failed for [email protected] – 550-Unrouteable address – 550 Sender verify failed (in reply to RCPT TO command)
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