Handle SmtpResponseException in DataCommand (#258)

Added a catch block for SmtpResponseException in DataCommand to return false when this exception occurs, improving error handling during SMTP data processing.

Author: tinohager

Src/SmtpServer/Protocol/DataCommand.cs

@@ -58,9 +58,14 @@ await context.Pipe.Input.ReadDotBlockAsync(
 
                 await context.Pipe.Output.WriteReplyAsync(response, cancellationToken).ConfigureAwait(false);
             }
+            catch (SmtpResponseException)
+            {
+                return false;
+            }
             catch (Exception)
             {
                 await context.Pipe.Output.WriteReplyAsync(new SmtpResponse(SmtpReplyCode.TransactionFailed), cancellationToken).ConfigureAwait(false);
+                return false;
             }
 
             return true;