In 2012, we posted a list of the world’s most popular SMTP response codes. We are now pleased to present an update to the list. Using a slightly updated script, we
- Processed email delivery logs from the MailChannels Cloud SMTP relay service;
- Picked up all the SMTP response messages representing permanent delivery failures;
- Did a bit of string cleaning to remove serial numbers and other random-looking identifiers; and,
- Associated each log line with the organization that generated the error.
Here are the top rejection messages
(organized by the network that generates the error)
| Organization | Response Code | Meaning |
| GoDaddy (secureserver.net) | 550 5.1.0 23.83.x.y is not allowed to send from <example.com> per it’s SPF Record. Please inspect your SPF settings, and try again. IB508 <http://x.co/srbounce> | The message was rejected because the sender domain (example.com) does not authorize the sending IP address in its SPF record. |
| 552 5.2.0 9qos1t0… – 9qos1t0… This message has been rejected due to content judged to be spam by the internet community IB212 – If you feel this is in error, please submit a request using the following page. <https://checkspam.secureserver.net/?sid=9qos1t0…> | GoDaddy’s spam filter thinks the message is spam. By clicking on the provided link, you can report the block as a false positive. | |
| AT&T (prodigy.net) | 553 5.3.0 alph135 DNSBL:ATTRBL 521< 23.83.x.y >_is_blocked.__For_information_see_http://att.net/blocks | AT&T’s spam filter has blocked your IP address. You can fill in a form provided by AT&T to request that your IP address be de-listed. |
| Yahoo (yahoo.com) | 554 delivery error: dd This user doesn’t have a yahoo.com account (example@yahoo.com) [0] – mta1012.mail.gq1.yahoo.com | The email address you’re trying to send email to does not exist. |
| 554 delivery error: dd Sorry your message toexample@yahoo.com cannot be delivered. This account has been disabled or discontinued [#102]. – mta1496.mail.bf1.yahoo.com | The email address you’re trying to send to has been disabled or discontinued. | |
| 554 5.7.9 Message not accepted for policy reasons. Seehttps://help.yahoo.com/kb/postmaster/SLN7253.html | Yahoo! has rejected your message for some other reason. | |
| 554 delivery error: dd This account has been temporarily suspended. Please try again later. – mta1102.mail.ir2.yahoo.com | Yahoo has temporarily disabled email for the recipient you are trying to reach. This may happen if an email recipient receives a great deal of spam. | |
| Endurance International Group (eigbox.net) | 550 <> Sender rejected. | A bounce generated by your mail server has been rejected by the receiving server to which the bounce was addressed. |
| Google (1e100.net) | 550 5.7.1 Unauthenticated email from yahoo.co.in is not accepted due to domain’s
550-5.7.1 DMARC policy. Please contact administrator of yahoo.co.in domain if 550-5.7.1 this was a legitimate mail. Please visit 550-5.7.1 https://support.google.com/mail/answer/2451690 to learn about DMARC 550 5.7.1 initiative. s140si61565….111 – gsmtp |
Google’s mail server has rejected your message because the domain of the sender address (yahoo.co.in in this example) has a DMARC policy that you have somehow violated. DMARC enables domain owners to control how email from their domain may be sent. For more information, visit the link provided by Google. |
| 552 5.7.0 This message was blocked because its content presents a potential
552-5.7.0 security issue. Please visit 552-5.7.0 https://support.google.com/mail/answer/6590to review our message 552 5.7.0 content and attachment content guidelines. c133si5731….145 – gsmtp |
Google’s mail server has rejected the message because it contains a file attachment that is of a “high risk” type. At present, Google prohibits the following types of attachments:
.ADE, .ADP, .BAT, .CHM, .CMD, .COM, .CPL, .EXE, .HTA, .INS, .ISP, .JAR, .JSE, .LIB, .LNK, .MDE, .MSC, .MSP, .MST, .PIF, .SCR, .SCT, .SHB, .SYS, .VB, .VBE, .VBS, .VXD, .WSC, .WSF, .WSH |
|
| 552 5.2.3 Your message exceeded Google’s message size limits. Please visit
552-5.2.3 https://support.google.com/mail/answer/6584#limit to view our size 552 5.2.3 guidelines. 198si450….22 – gsmtp |
Google does not accept attachments that are larger than 25MB in size. In some situations, smaller attachments may also be rejected. | |
| 550 5.7.1 [23.83.x.y 7] Our system has detected that this message is
550-5.7.1 likely unsolicited mail. To reduce the amount of spam sent to Gmail, 550-5.7.1 this message has been blocked. Please visit 550 5.7.1 https://support.google.com/mail/answer/188131for more information. x8si4242….230 – gsmtp |
Google’s spam filter has determined your message is spam, and has decided to reject it rather than put it in the recipient’s spam folder. | |
| 550 5.7.1 [23.83.209.23 11] Our system has detected that this message is
550-5.7.1 not RFC 5322 compliant. To reduce the amount of spam sent to Gmail, 550-5.7.1 this message has been blocked. Please review 550 5.7.1 RFC 5322 specifications for more information. vw4si4702….180 – gsmtp |
Google blocks messages which are not strictly compliant with the RFC 5322 message format. | |
| 550 5.7.1 Please update the address to @example.com and try again. – gcdp j9si4733….36 – gsmtp | The recipient you’re trying to reach has moved to a new domain. To fix this problem, you need to update the recipient address to use the new domain suggested (in this example, “example.com”). | |
| Microsoft (outlook.com, hotmail.com) | 550 5.7.0 (COL004-MC2F47) Message could not be delivered. Please ensure the message is RFC 5322 compliant. | Microsoft insists that your message be fully compliant with the RFC 5322 message format. |
| 550 5.7.0 (BAY004-MC5F13) Unfortunately, messages from (23.83.x.y) on behalf of (example.com) could not be delivered due to domain owner policy restrictions. | Your message was rejected because the sender’s domain name (e.g. example.com) does not permit delivering email from your mail server. Use the SPF record testing tool to find out why. |
