Why are IPs listed as blocked on SNDS with no Microsoft bounces?

Marketer from Email Geeks explains he has a customer with IPs listed as blocked by SNDS for a long time, but had been delivering fine until recently. Also, mentions IPs listed as blocked that haven't sent email in years.

Marketer from Email Geeks agrees that Microsoft's systems often contradict themselves and don't make sense.

Marketer from Email Geeks explains there can be false information in SNDS, citing an example of a customer with a good open rate being listed as blocked for a long time despite resolved issues.

Email marketer from Stackoverflow explains that the sender's IPs being blocked by SNDS can be due to issues with authentication (SPF, DKIM, DMARC) or poor sender reputation.

Email marketer from EmailDudes shares that factors like sudden sending volume spikes, a high rate of complaints from email users, or sending spam-like emails can make SNDS mark you as blocked. These blocks can happen independently of the bounce messages.

Marketer from Email Geeks shares that Hotmail's data can be inconsistent, sometimes showing bounces without listing IPs as blocked and vice versa. Suggesting Microsoft services can be unreliable.

Email marketer from Webmaster World explains that SNDS data can be delayed or inaccurate. He suggests checking the actual bounce messages in your logs as the most reliable source of information. A discrepancy could mean Microsoft is filtering but not bouncing.

Email marketer from Reddit notes that SNDS data isn't always real-time or perfectly accurate, especially concerning spam complaints. They recommend cross-referencing with other feedback loops and your own sending data.

Email marketer from Mailjet responds that SNDS can indicate potential delivery issues even without explicit bounces. This can result from filtering, greylisting or reputation-based blocking before a bounce message is generated.

Email marketer from Reddit responds that it can be related to spam traps, which would affect your IP reputation and lead to blocking by Microsoft's systems without a hard bounce.

Email marketer from Experts Exchange believes that you need to check if you are on any RBL's, as some can cause Microsoft to block you even without seeing the bounces

Email marketer from Stackoverflow says that Microsoft might be blocking emails based on spam complaints even if you don't see the bounces. The Hotmail servers will mark you as blocked but you need to actively look in SNDS to see the IP Address blocked

Marketer from Email Geeks shares that seeing IPs listed as “blocked” on SNDS without corresponding Microsoft bounces often indicates users marking emails as spam and suggests submitting a support ticket to Microsoft.

Email marketer from Glock Apps shares a possible reason for SNDS blocking is due to Microsoft potentially filtering the emails into the junk mail, which would not cause a bounce.

Expert from Spam Resource shares that the IPs listed in SNDS are usually due to hitting spam traps, and this can be different from IPs that generate bounces because the deliverability and reputation damage causes the IPs to be blocked.

Expert from Word to the Wise explains that SNDS data reflects Microsoft's internal filtering decisions, which can be based on factors beyond hard bounce criteria, such as sender reputation or spam complaints. As such, mail may be filtered without a bounce being generated.

Documentation from Microsoft explains that SNDS data reflects their internal reputation assessment of sending IPs. This reputation can affect filtering decisions before hard bounces are issued, which might result from spam complaints or other factors that impact reputation.

Documentation from Microsoft explains that a 'blocked' status in SNDS indicates Microsoft is actively filtering mail from that IP address. They may not always generate a hard bounce if the mail is simply being filtered to junk or deleted.

Documentation from RFC specifies that not all delivery failures result in a hard bounce with a specific SMTP error code. Some can be handled silently by the receiving server based on pre-configured filtering rules.

Documentation from Google states that a low domain or IP reputation can cause emails to be marked as spam rather than bounced, especially if the email content also triggers spam filters.

Documentation from SparkPost shares that discrepancies between SNDS data and observed bounce rates can occur because Microsoft's filters can reject messages based on factors beyond hard bounce criteria, such as content or overall sender reputation, resulting in silent filtering and no explicit bounces.