v3Refactor SMTP Auth Error Handling

diff --git a/git-send-email.perl b/git-send-email.perl
index a012d61abb..532dda264c 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1411,7 +1411,7 @@ sub smtp_auth_maybe {
 	eval {
 		require Authen::SASL;
 		Authen::SASL->import(qw(Perl));
-	};
+	}

 	# Check mechanism naming as defined in:
 	# https://tools.ietf.org/html/rfc4422#page-8
@@ -1426,42 +1426,56 @@ sub smtp_auth_maybe {
 		'protocol' => 'smtp',
 		'host' => smtp_host_string(),
 		'username' => $smtp_authuser,
+		# if there's no password, "git credential fill" will
+		# give us one, otherwise it'll just pass this one.
 		'password' => $smtp_authpass
-
 	}, sub {
 		my $cred = shift;
 		my $result;
 		my $error;
-		if ($smtp_auth) {
-			my $sasl = Authen::SASL->new(
-				mechanism => $smtp_auth,
-				callback => {
-					user => $cred->{'username'},
-					pass => $cred->{'password'},
-					authname => $cred->{'username'},
-				}
-			);
-			return !!$smtp->auth($sasl);
-		} else {
-			# Handle plain authentication errors
-			eval {
+
+		# catch all SMTP auth error
+		eval {
+			if ($smtp_auth) {
+				my $sasl = Authen::SASL->new(
+					mechanism => $smtp_auth,
+					callback => {
+						user => $cred->{'username'},
+						pass => $cred->{'password'},
+						authname => $cred->{'username'},
+					}
+				);
+				$result = $smtp->auth($sasl);
+			} else {
 				$result = $smtp->auth($cred->{'username'}, $cred->{'password'});
-				1; # Ensure true value is returned
-			} or do {
-				$error = $@ || 'Unknown error';
-			};
-		}
-		# Unified error handling logic
+			}
+			1; # Ensure true value is returned if no exception is thrown.
+		} or do {
+			$error = $@ || 'Unknown error';
+		};
+
+		#check if an error was captured
 		if ($error) {
-			# Match temporary errors
-			if ($error =~ /timeout|temporary|greylist|throttled|quota\s+exceeded|queue|overload|try\s+again|connection\s+lost|network\s+error/i) {
-				warn "SMTP temporary error: $error";
-				return 1;
+			#Parse SMTP status code from error message in:
+			#https://www.rfc-editor.org/rfc/rfc5321.html
+			if ($error =~ /\b(\d{3})\b/) {
+				my $status_code = $1;
+				if ($status_code =~ /^4/) {
+					# 4yz: Transient Negative Completion reply
+					warn "SMTP temporary error (status code $status_code): $error";
+					return 1;
+				} elsif ($status_code =~ /^5/) {
+					# 5yz: Permanent Negative Completion reply
+					warn "SMTP permanent error (status code $status_code): $error";
+					return 0;
+				}
+				# If no status code is found, treat as permanent error
+				warn "SMTP unknown error: $error";
+				return 0;
 			}
-			return 0;
-		}
-		return !!$result;
-	});
+			return $result ? 1 : 0;
+		});
+
 	return $auth;
 }

--
2.49.0.rc0.57.gdb91954e18

diff --git a/git-send-email.perl b/git-send-email.perl
index 798d59b84f..8feb43e9f7 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1419,7 +1419,7 @@ sub smtp_auth_maybe {
 		die "invalid smtp auth: '${smtp_auth}'";
 	}

-	# TODO: Authentication may fail not because credentials were
+	# Authentication may fail not because credentials were
 	# invalid but due to other reasons, in which we should not
 	# reject credentials.
 	$auth = Git::credential({
@@ -1431,25 +1431,32 @@ sub smtp_auth_maybe {
 		'password' => $smtp_authpass
 	}, sub {
 		my $cred = shift;
+		my $result;
+		my $error;
+
+		# catch all SMTP auth error in a unified eval block
+		eval {
+			if ($smtp_auth) {
+				my $sasl = Authen::SASL->new(
+					mechanism => $smtp_auth,
+					callback => {
+						user     => $cred->{'username'},
+						pass     => $cred->{'password'},
+						authname => $cred->{'username'},
+					}
+				);
+				$result = $smtp->auth($sasl);
+			} else {
+				$result = $smtp->auth($cred->{'username'}, $cred->{'password'});
+			}
+			1; # ensure true value is returned if no exception is thrown
+		} or do {
+			$error = $@ || 'Unknown error';
+		};

-		if ($smtp_auth) {
-			my $sasl = Authen::SASL->new(
-				mechanism => $smtp_auth,
-				callback => {
-					user => $cred->{'username'},
-					pass => $cred->{'password'},
-					authname => $cred->{'username'},
-				}
-			);
-
-			return !!$smtp->auth($sasl);
-		}
-
-		return !!$smtp->auth($cred->{'username'}, $cred->{'password'});
-	});
-
-	return $auth;
-}
+		# NOTE: SMTP status code handling will be added in a subsequent commit
+		return $result ? 1 : 0;
+	}

 sub ssl_verify_params {
 	eval {
--
2.48.1

diff --git a/git-send-email.perl b/git-send-email.perl
index 8feb43e9f7..69ba328653 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1454,9 +1454,30 @@ sub smtp_auth_maybe {
 			$error = $@ || 'Unknown error';
 		};

-		# NOTE: SMTP status code handling will be added in a subsequent commit
-		return $result ? 1 : 0;
-	}
+		# check if an error was captured
+		if ($error) {
+			# parse SMTP status code from error message in:
+			# https://www.rfc-editor.org/rfc/rfc5321.html
+			if ($error =~ /\b(\d{3})\b/) {
+				my $status_code = $1;
+				if ($status_code =~ /^4/) {
+					# 4yz: Transient Negative Completion reply
+					warn "SMTP temporary error (status code $status_code): $error";
+					return 1;
+				} elsif ($status_code =~ /^5/) {
+					# 5yz: Permanent Negative Completion reply
+					warn "SMTP permanent error (status code $status_code): $error";
+					return 0;
+				}
+				# if no recognized status code is found, treat as permanent error
+				warn "SMTP unknown error: $error";
+				return 0;
+			}
+			return $result ? 1 : 0;
+		} else {
+			return $result ? 1 : 0;
+		}
+}

 sub ssl_verify_params {
 	eval {
--
2.48.1

diff --git a/git-send-email.perl b/git-send-email.perl
index 798d59b84f..8feb43e9f7 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1419,7 +1419,7 @@ sub smtp_auth_maybe {
 		die "invalid smtp auth: '${smtp_auth}'";
 	}

-	# TODO: Authentication may fail not because credentials were
+	# Authentication may fail not because credentials were
 	# invalid but due to other reasons, in which we should not
 	# reject credentials.
 	$auth = Git::credential({
@@ -1431,25 +1431,32 @@ sub smtp_auth_maybe {
 		'password' => $smtp_authpass
 	}, sub {
 		my $cred = shift;
+		my $result;
+		my $error;
+
+		# catch all SMTP auth error in a unified eval block
+		eval {
+			if ($smtp_auth) {
+				my $sasl = Authen::SASL->new(
+					mechanism => $smtp_auth,
+					callback => {
+						user     => $cred->{'username'},
+						pass     => $cred->{'password'},
+						authname => $cred->{'username'},
+					}
+				);
+				$result = $smtp->auth($sasl);
+			} else {
+				$result = $smtp->auth($cred->{'username'}, $cred->{'password'});
+			}
+			1; # ensure true value is returned if no exception is thrown
+		} or do {
+			$error = $@ || 'Unknown error';
+		};

-		if ($smtp_auth) {
-			my $sasl = Authen::SASL->new(
-				mechanism => $smtp_auth,
-				callback => {
-					user => $cred->{'username'},
-					pass => $cred->{'password'},
-					authname => $cred->{'username'},
-				}
-			);
-
-			return !!$smtp->auth($sasl);
-		}
-
-		return !!$smtp->auth($cred->{'username'}, $cred->{'password'});
-	});
-
-	return $auth;
-}
+		# NOTE: SMTP status code handling will be added in a subsequent commit
+		return $result ? 1 : 0;
+	}

 sub ssl_verify_params {
 	eval {
--
2.48.1

diff --git a/git-send-email.perl b/git-send-email.perl
index 8feb43e9f7..69ba328653 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1454,9 +1454,30 @@ sub smtp_auth_maybe {
 			$error = $@ || 'Unknown error';
 		};

-		# NOTE: SMTP status code handling will be added in a subsequent commit
-		return $result ? 1 : 0;
-	}
+		# check if an error was captured
+		if ($error) {
+			# parse SMTP status code from error message in:
+			# https://www.rfc-editor.org/rfc/rfc5321.html
+			if ($error =~ /\b(\d{3})\b/) {
+				my $status_code = $1;
+				if ($status_code =~ /^4/) {
+					# 4yz: Transient Negative Completion reply
+					warn "SMTP temporary error (status code $status_code): $error";
+					return 1;
+				} elsif ($status_code =~ /^5/) {
+					# 5yz: Permanent Negative Completion reply
+					warn "SMTP permanent error (status code $status_code): $error";
+					return 0;
+				}
+				# if no recognized status code is found, treat as permanent error
+				warn "SMTP unknown error: $error";
+				return 0;
+			}
+			return $result ? 1 : 0;
+		} else {
+			return $result ? 1 : 0;
+		}
+}

 sub ssl_verify_params {
 	eval {
--
2.48.1

diff --git a/git-send-email.perl b/git-send-email.perl
index 798d59b84f..8feb43e9f7 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1419,7 +1419,7 @@ sub smtp_auth_maybe {
 		die "invalid smtp auth: '${smtp_auth}'";
 	}

-	# TODO: Authentication may fail not because credentials were
+	# Authentication may fail not because credentials were
 	# invalid but due to other reasons, in which we should not
 	# reject credentials.
 	$auth = Git::credential({
@@ -1431,25 +1431,32 @@ sub smtp_auth_maybe {
 		'password' => $smtp_authpass
 	}, sub {
 		my $cred = shift;
+		my $result;
+		my $error;
+
+		# catch all SMTP auth error in a unified eval block
+		eval {
+			if ($smtp_auth) {
+				my $sasl = Authen::SASL->new(
+					mechanism => $smtp_auth,
+					callback => {
+						user     => $cred->{'username'},
+						pass     => $cred->{'password'},
+						authname => $cred->{'username'},
+					}
+				);
+				$result = $smtp->auth($sasl);
+			} else {
+				$result = $smtp->auth($cred->{'username'}, $cred->{'password'});
+			}
+			1; # ensure true value is returned if no exception is thrown
+		} or do {
+			$error = $@ || 'Unknown error';
+		};

-		if ($smtp_auth) {
-			my $sasl = Authen::SASL->new(
-				mechanism => $smtp_auth,
-				callback => {
-					user => $cred->{'username'},
-					pass => $cred->{'password'},
-					authname => $cred->{'username'},
-				}
-			);
-
-			return !!$smtp->auth($sasl);
-		}
-
-		return !!$smtp->auth($cred->{'username'}, $cred->{'password'});
-	});
-
-	return $auth;
-}
+		# NOTE: SMTP status code handling will be added in a subsequent commit
+		return $result ? 1 : 0;
+	}

 sub ssl_verify_params {
 	eval {
--
2.48.1

diff --git a/git-send-email.perl b/git-send-email.perl
index 8feb43e9f7..69ba328653 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1454,9 +1454,30 @@ sub smtp_auth_maybe {
 			$error = $@ || 'Unknown error';
 		};
 
-		# NOTE: SMTP status code handling will be added in a subsequent commit
-		return $result ? 1 : 0;
-	}
+		# check if an error was captured
+		if ($error) {
+			# parse SMTP status code from error message in:
+			# https://www.rfc-editor.org/rfc/rfc5321.html
+			if ($error =~ /\b(\d{3})\b/) {
+				my $status_code = $1;
+				if ($status_code =~ /^4/) {
+					# 4yz: Transient Negative Completion reply
+					warn "SMTP temporary error (status code $status_code): $error";
+					return 1;
+				} elsif ($status_code =~ /^5/) {
+					# 5yz: Permanent Negative Completion reply
+					warn "SMTP permanent error (status code $status_code): $error";
+					return 0;
+				}
+				# if no recognized status code is found, treat as permanent error
+				warn "SMTP unknown error: $error";
+				return 0;
+			}
+			return $result ? 1 : 0;
+		} else {
+			return $result ? 1 : 0;
+		}
+}
 
 sub ssl_verify_params {
 	eval {

diff --git a/git-send-email.perl b/git-send-email.perl
index 798d59b84f..0f05f55e50 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1419,7 +1419,7 @@ sub smtp_auth_maybe {
 		die "invalid smtp auth: '${smtp_auth}'";
 	}
 
-	# TODO: Authentication may fail not because credentials were
+	# Authentication may fail not because credentials were
 	# invalid but due to other reasons, in which we should not
 	# reject credentials.
 	$auth = Git::credential({
@@ -1431,21 +1431,32 @@ sub smtp_auth_maybe {
 		'password' => $smtp_authpass
 	}, sub {
 		my $cred = shift;
-
-		if ($smtp_auth) {
-			my $sasl = Authen::SASL->new(
-				mechanism => $smtp_auth,
-				callback => {
-					user => $cred->{'username'},
-					pass => $cred->{'password'},
-					authname => $cred->{'username'},
-				}
-			);
-
-			return !!$smtp->auth($sasl);
-		}
-
-		return !!$smtp->auth($cred->{'username'}, $cred->{'password'});
+		my $result;
+		my $error;
+
+		# catch all SMTP auth error in a unified eval block
+		eval {
+			if ($smtp_auth) {
+				my $sasl = Authen::SASL->new(
+					mechanism => $smtp_auth,
+					callback => {
+						user     => $cred->{'username'},
+						pass     => $cred->{'password'},
+						authname => $cred->{'username'},
+					}
+				);
+				$result = $smtp->auth($sasl);
+			} else {
+				$result = $smtp->auth($cred->{'username'}, $cred->{'password'});
+			}
+			1; # ensure true value is returned if no exception is thrown
+		} or do {
+			$error = $@ || 'Unknown error';
+		};
+
+		# NOTE: SMTP status code handling will be added in a subsequent commit,
+		# return 1 when failed due to non-credential reasons
+		return $error ? 1 : ($result ? 1 : 0);
 	});
 
 	return $auth;

diff --git a/git-send-email.perl b/git-send-email.perl
index 0f05f55e50..e09a4a316f 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1454,9 +1454,38 @@ sub smtp_auth_maybe {
 			$error = $@ || 'Unknown error';
 		};
 
-		# NOTE: SMTP status code handling will be added in a subsequent commit,
-		# return 1 when failed due to non-credential reasons
-		return $error ? 1 : ($result ? 1 : 0);
+		if ($error) {
+			# check if an error was captured
+			# parse SMTP status code from error message in:
+			# https://www.rfc-editor.org/rfc/rfc5321.html
+			if ($error =~ /\b(\d{3})\b/) {
+				my $status_code = $1;
+				if ($status_code =~ /^4/) {
+					# 4yz: Transient Negative Completion reply
+					warn "SMTP temporary error (status code $status_code): $error";
+					return 1;
+				} elsif ($status_code =~ /^5/) {
+					# 5yz: Permanent Negative Completion reply
+					warn "SMTP permanent error (status code $status_code): $error";
+					return 0;
+				} else {
+					# if no recognized status code is found, treat as transient error
+					warn "SMTP unknown error: $error. Treating as permanent failure.";
+					return 1;
+				}
+			} else {
+				# if no status code is found, treat as transient error
+				warn "SMTP generic error: $error";
+				return 1;
+			}
+		} elsif (!defined $result) {
+			# if no error and no result is returned, treat as transient error
+			warn "SMTP no result error: $error";
+		    return 1; 
+		}
+		else {
+			return $result ? 1 : 0;
+		}
 	});
 
 	return $auth;

diff --git a/git-send-email.perl b/git-send-email.perl
index 798d59b84f..0f05f55e50 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1419,7 +1419,7 @@ sub smtp_auth_maybe {
 		die "invalid smtp auth: '${smtp_auth}'";
 	}
 
-	# TODO: Authentication may fail not because credentials were
+	# Authentication may fail not because credentials were
 	# invalid but due to other reasons, in which we should not
 	# reject credentials.
 	$auth = Git::credential({
@@ -1431,21 +1431,32 @@ sub smtp_auth_maybe {
 		'password' => $smtp_authpass
 	}, sub {
 		my $cred = shift;
-
-		if ($smtp_auth) {
-			my $sasl = Authen::SASL->new(
-				mechanism => $smtp_auth,
-				callback => {
-					user => $cred->{'username'},
-					pass => $cred->{'password'},
-					authname => $cred->{'username'},
-				}
-			);
-
-			return !!$smtp->auth($sasl);
-		}
-
-		return !!$smtp->auth($cred->{'username'}, $cred->{'password'});
+		my $result;
+		my $error;
+
+		# catch all SMTP auth error in a unified eval block
+		eval {
+			if ($smtp_auth) {
+				my $sasl = Authen::SASL->new(
+					mechanism => $smtp_auth,
+					callback => {
+						user     => $cred->{'username'},
+						pass     => $cred->{'password'},
+						authname => $cred->{'username'},
+					}
+				);
+				$result = $smtp->auth($sasl);
+			} else {
+				$result = $smtp->auth($cred->{'username'}, $cred->{'password'});
+			}
+			1; # ensure true value is returned if no exception is thrown
+		} or do {
+			$error = $@ || 'Unknown error';
+		};
+
+		# NOTE: SMTP status code handling will be added in a subsequent commit,
+		# return 1 when failed due to non-credential reasons
+		return $error ? 1 : ($result ? 1 : 0);
 	});
 
 	return $auth;

diff --git a/git-send-email.perl b/git-send-email.perl
index 0f05f55e50..12b1a7c7de 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1454,14 +1454,42 @@ sub smtp_auth_maybe {
 			$error = $@ || 'Unknown error';
 		};
 
-		# NOTE: SMTP status code handling will be added in a subsequent commit,
-		# return 1 when failed due to non-credential reasons
-		return $error ? 1 : ($result ? 1 : 0);
+		return handle_smtp_error($error, $result);
 	});
 
 	return $auth;
 }
 
+sub handle_smtp_error {
+	my ($error, $result) = @_;
+
+	# If no error is present, return the result directly
+	return $result ? 1 : 0 unless $error;
+
+	# Check if an error was captured
+	# Parse SMTP status code from error message in:
+	# https://www.rfc-editor.org/rfc/rfc5321.html
+	if ($error =~ /\b(\d{3})\b/) {
+		my $status_code = $1;
+		if ($status_code =~ /^4/) {
+			# 4yz: Transient Negative Completion reply
+			warn "SMTP transient error (status code $status_code): $error";
+			return 1;
+		} elsif ($status_code =~ /^5/) {
+			# 5yz: Permanent Negative Completion reply
+			warn "SMTP permanent error (status code $status_code): $error";
+			return 0;
+		}
+		# If no recognized status code is found, treat as transient error
+		warn "SMTP unknown error: $error. Treating as transient failure.";
+		return 1;
+	}
+
+	# If no status code is found, treat as transient error
+	warn "SMTP generic error: $error";
+	return 1;
+}
+
 sub ssl_verify_params {
 	eval {
 		require IO::Socket::SSL;

diff --git a/git-send-email.perl b/git-send-email.perl
index 798d59b84f..0f05f55e50 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1419,7 +1419,7 @@ sub smtp_auth_maybe {
 		die "invalid smtp auth: '${smtp_auth}'";
 	}
 
-	# TODO: Authentication may fail not because credentials were
+	# Authentication may fail not because credentials were
 	# invalid but due to other reasons, in which we should not
 	# reject credentials.
 	$auth = Git::credential({
@@ -1431,21 +1431,32 @@ sub smtp_auth_maybe {
 		'password' => $smtp_authpass
 	}, sub {
 		my $cred = shift;
-
-		if ($smtp_auth) {
-			my $sasl = Authen::SASL->new(
-				mechanism => $smtp_auth,
-				callback => {
-					user => $cred->{'username'},
-					pass => $cred->{'password'},
-					authname => $cred->{'username'},
-				}
-			);
-
-			return !!$smtp->auth($sasl);
-		}
-
-		return !!$smtp->auth($cred->{'username'}, $cred->{'password'});
+		my $result;
+		my $error;
+
+		# catch all SMTP auth error in a unified eval block
+		eval {
+			if ($smtp_auth) {
+				my $sasl = Authen::SASL->new(
+					mechanism => $smtp_auth,
+					callback => {
+						user     => $cred->{'username'},
+						pass     => $cred->{'password'},
+						authname => $cred->{'username'},
+					}
+				);
+				$result = $smtp->auth($sasl);
+			} else {
+				$result = $smtp->auth($cred->{'username'}, $cred->{'password'});
+			}
+			1; # ensure true value is returned if no exception is thrown
+		} or do {
+			$error = $@ || 'Unknown error';
+		};
+
+		# NOTE: SMTP status code handling will be added in a subsequent commit,
+		# return 1 when failed due to non-credential reasons
+		return $error ? 1 : ($result ? 1 : 0);
 	});
 
 	return $auth;

diff --git a/git-send-email.perl b/git-send-email.perl
index 0f05f55e50..1f613fa979 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -1454,14 +1454,40 @@ sub smtp_auth_maybe {
 			$error = $@ || 'Unknown error';
 		};
 
-		# NOTE: SMTP status code handling will be added in a subsequent commit,
-		# return 1 when failed due to non-credential reasons
-		return $error ? 1 : ($result ? 1 : 0);
+		return ($error
+			? handle_smtp_error($error)
+			: ($result ? 1 : 0));
 	});
 
 	return $auth;
 }
 
+sub handle_smtp_error {
+	my ($error) = @_;
+
+	# Parse SMTP status code from error message in:
+	# https://www.rfc-editor.org/rfc/rfc5321.html
+	if ($error =~ /\b(\d{3})\b/) {
+		my $status_code = $1;
+		if ($status_code =~ /^4/) {
+			# 4yz: Transient Negative Completion reply
+			warn "SMTP transient error (status code $status_code): $error";
+			return 1;
+		} elsif ($status_code =~ /^5/) {
+			# 5yz: Permanent Negative Completion reply
+			warn "SMTP permanent error (status code $status_code): $error";
+			return 0;
+		}
+		# If no recognized status code is found, treat as transient error
+		warn "SMTP unknown error: $error. Treating as transient failure.";
+		return 1;
+	}
+
+	# If no status code is found, treat as transient error
+	warn "SMTP generic error: $error";
+	return 1;
+}
+
 sub ssl_verify_params {
 	eval {
 		require IO::Socket::SSL;