Update the release notes #296

ChangeLog.md

@@ -3,7 +3,7 @@ RELEASE NOTES for Ruby version of Sisimai
 - releases: "https://github.com/sisimai/rb-sisimai/releases"
 - download: "https://rubygems.org/gems/sisimai"
 
-v5.0.3p2
+v5.0.3p3
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 - release: ""
 - version: ""
@@ -34,6 +34,7 @@ v5.0.3p2
     - Follow any updates of the SMTP error code and message list in each email services related to
       `AuthFailure`, `BadReputation`, `RequirePTR`, and other error reasons added at v5
     - No longer needed method `Sisimai::Rhost.match` method has been removed
+  - #296 Add 8 sample emails generated by OpenSMTPD 6.8.0p2
 
 v5.0.3
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