Throw derived ResendRateLimitExceededException.

src/Resend/IHasRateLimit.cs

@@ -0,0 +1,7 @@
+namespace Resend
+{
+    public interface IHasRateLimit
+    {
+        ResendRateLimit? Limits { get; }
+    }
+}

src/Resend/ResendClient.cs

@@ -470,6 +470,10 @@ private async Task<ResendResponse> Execute( HttpRequestMessage req, Cancellation
 
             if ( err == null )
                 ex = new ResendException( resp.StatusCode, ErrorType.MissingResponse, "Missing error response" );
+            else if ( err.ErrorType == ErrorType.RateLimitExceeded )
+            {
+                ex = new ResendRateLimitExceededException( HttpStatusCode.TooManyRequests, err.Message, rrl );
+            }
             else
                 ex = new ResendException( (HttpStatusCode) err.StatusCode, err.ErrorType, err.Message );
 
@@ -551,6 +555,10 @@ private async Task<ResendResponse<T2>> Execute<T1, T2>( HttpRequestMessage req,
 
             if ( err == null )
                 ex = new ResendException( resp.StatusCode, ErrorType.MissingResponse, "Missing error response" );
+            else if ( err.ErrorType == ErrorType.RateLimitExceeded )
+            {
+                ex = new ResendRateLimitExceededException( HttpStatusCode.TooManyRequests, err.Message, rrl );
+            }
             else
                 ex = new ResendException( (HttpStatusCode) err.StatusCode, err.ErrorType, err.Message );
 
@@ -625,7 +633,8 @@ private async Task<ResendResponse<T2>> Execute<T1, T2>( HttpRequestMessage req,
         return new ResendResponse<T2>( res, rrl );
     }
 
-
+    /// <summary>
+    /// Rate limit info from the HTTP response headers.
     /// <summary />
     private ResendRateLimit FromHeaders( HttpResponseHeaders headers )
     {

src/Resend/ResendClientOptions.cs

@@ -1,24 +1,24 @@
-namespace Resend;
-
-/// <summary />
-public class ResendClientOptions
-{
-    /// <summary>
-    /// Base URL for Resend API.
-    /// </summary>
-    /// <remarks>
-    /// Default is `https://api.resend.com`.
-    /// </remarks>
-    public string ApiUrl { get; set; } = "https://api.resend.com";
-
-    /// <summary>
-    /// API key token.
-    /// </summary>
-    public string ApiToken { get; set; } = default!;
-
-    /// <summary>
-    /// Whether exceptions should be thrown when the API invocation
-    /// fails (for whatever reason).
-    /// </summary>
-    public bool ThrowExceptions { get; set; } = true;
-}
+namespace Resend;
+
+/// <summary />
+public class ResendClientOptions
+{
+    /// <summary>
+    /// Base URL for Resend API.
+    /// </summary>
+    /// <remarks>
+    /// Default is `https://api.resend.com`.
+    /// </remarks>
+    public string ApiUrl { get; set; } = "https://api.resend.com";
+
+    /// <summary>
+    /// API key token.
+    /// </summary>
+    public string ApiToken { get; set; } = default!;
+
+    /// <summary>
+    /// Whether exceptions should be thrown when the API invocation
+    /// fails (for whatever reason).
+    /// </summary>
+    public bool ThrowExceptions { get; set; } = true;
+}

src/Resend/ResendRateLimitExceededException.cs

@@ -0,0 +1,32 @@
+using System.Net;
+
+namespace Resend;
+
+/// <summary>
+/// Status code 429. User has hit their rate limit and should wait before resending the request.
+/// <summary />
+public class ResendRateLimitExceededException : ResendException, IHasRateLimit
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="ResendRateLimitExceededException"/> class.
+    /// <summary />
+    public ResendRateLimitExceededException( HttpStatusCode? statusCode, string message, ResendRateLimit? rateLimit )
+        : base( statusCode, ErrorType.RateLimitExceeded, message )
+    {
+        this.Limits = rateLimit;
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="ResendRateLimitExceededException"/> class.
+    /// <summary />
+    public ResendRateLimitExceededException( HttpStatusCode? statusCode, string message, Exception? innerException, ResendRateLimit? rateLimit )
+        : base( statusCode, ErrorType.RateLimitExceeded, message, innerException )
+    {
+        this.Limits = rateLimit;
+    }
+
+    /// <summary>
+    /// Gets the rate limit information from the response headers.
+    /// <summary />
+    public ResendRateLimit? Limits { get; }
+}