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Soverin’s SMTP servers use a set of proprietary error codes (each beginning with “S”) to indicate various delivery-related conditions. Whenever a client (MUA/MTA) attempts to send a message through Soverin, the server may respond with one of these codes—alongside a standard SMTP reply text—to signal exactly why a message was deferred, rejected, or temporarily refused.

Every code follows the format SXYZ, where:

• S denotes “Soverin.”

• The first digit (X) broadly indicates a category:

  • 0 → Rate limits (throttling).

  • 1 → External abuse lists / IP blocklists.

  • 3 → Internal blocking policies.

• The next two digits (Y and Z) provide a more specific sub-condition within that category.

Below you’ll find a table listing each code (for now, using the example set you provided). Once the full table is finalized, you can expand or refine individual descriptions as needed.

Example 1: Table format

Code	Category	Short description
S000	Rate limit	General rate-limit exceeded; too many commands or connections in a short interval.
S001	Rate limit	Daily/hourly message-submission limit reached for this account or IP.
S011	External Abuse List	?
S012	External Abuse List	?
S112	External Abuse List	Cloudmark has detected unusual amount of bad reports from your IP or domain. Read more information about S112 and Cloudmark
S113	External IP Blocklist	?
S115	External IP Blocklist	?
S301	Internal Abuse	?
S302	Internal Abuse	?
S303	Internal Abuse	?
S391	Internal Abuse	?
S392	Internal Abuse	?
S393	Internal Abuse	?

Example 2: Paragraph format

S000 - S009

Rate-limit exceeded; too many commands or connections in a short interval. Todo: More text and explanations.

S011 - S019

Your IP or Domain is listed on an external blocklist. Todo: More text and explanations.

S111 - S119

Your IP or Domain is listed on an external blocklist. Todo: More text and explanations.

S300 - S399

Internal Abuse. Todo: More text and explanations.