diff --git a/hutool-core/src/main/java/cn/hutool/core/math/NumberUtil.java b/hutool-core/src/main/java/cn/hutool/core/math/NumberUtil.java
index de82d094a..575f8a9e0 100644
--- a/hutool-core/src/main/java/cn/hutool/core/math/NumberUtil.java
+++ b/hutool-core/src/main/java/cn/hutool/core/math/NumberUtil.java
@@ -1242,12 +1242,13 @@ public class NumberUtil {
 	 * @return 是否为整数
 	 */
 	public static boolean isInteger(final String s) {
-		if(StrUtil.isNotBlank(s)) {
-			try {
-				Integer.parseInt(s);
-			} catch (final NumberFormatException e) {
-				return false;
-			}
+		if(StrUtil.isBlank(s)) {
+			return false;
+		}
+		try {
+			Integer.parseInt(s);
+		} catch (final NumberFormatException e) {
+			return false;
 		}
 		return true;
 	}
@@ -1261,12 +1262,13 @@ public class NumberUtil {
 	 * @since 4.0.0
 	 */
 	public static boolean isLong(final String s) {
-		if (StrUtil.isNotBlank(s)) {
-			try {
-				Long.parseLong(s);
-			} catch (final NumberFormatException e) {
-				return false;
-			}
+		if(StrUtil.isBlank(s)) {
+			return false;
+		}
+		try {
+			Long.parseLong(s);
+		} catch (final NumberFormatException e) {
+			return false;
 		}
 		return true;
 	}
@@ -1278,15 +1280,16 @@ public class NumberUtil {
 	 * @return 是否为{@link Double}类型
 	 */
 	public static boolean isDouble(final String s) {
-		if (StrUtil.isNotBlank(s)) {
-			try {
-				Double.parseDouble(s);
-				return s.contains(".");
-			} catch (final NumberFormatException ignore) {
-				// ignore
-			}
+		if(StrUtil.isBlank(s)) {
+			return false;
 		}
-		return false;
+		try {
+			Double.parseDouble(s);
+			return s.contains(".");
+		} catch (final NumberFormatException ignore) {
+			// ignore
+		}
+		return true;
 	}
 
 	/**
diff --git a/hutool-core/src/test/java/cn/hutool/core/util/NumberUtilTest.java b/hutool-core/src/test/java/cn/hutool/core/util/NumberUtilTest.java
index 2b5d0c6bd..d3607ce39 100644
--- a/hutool-core/src/test/java/cn/hutool/core/util/NumberUtilTest.java
+++ b/hutool-core/src/test/java/cn/hutool/core/util/NumberUtilTest.java
@@ -62,6 +62,9 @@ public class NumberUtilTest {
 		Assert.assertTrue(NumberUtil.isInteger("0256"));
 		Assert.assertTrue(NumberUtil.isInteger("0"));
 		Assert.assertFalse(NumberUtil.isInteger("23.4"));
+		Assert.assertFalse(NumberUtil.isInteger(null));
+		Assert.assertFalse(NumberUtil.isInteger(""));
+		Assert.assertFalse(NumberUtil.isInteger(" "));
 	}
 
 	@Test
@@ -71,6 +74,9 @@ public class NumberUtilTest {
 		Assert.assertTrue(NumberUtil.isLong("0256"));
 		Assert.assertTrue(NumberUtil.isLong("0"));
 		Assert.assertFalse(NumberUtil.isLong("23.4"));
+		Assert.assertFalse(NumberUtil.isLong(null));
+		Assert.assertFalse(NumberUtil.isLong(""));
+		Assert.assertFalse(NumberUtil.isLong(" "));
 	}
 
 	@Test
diff --git a/hutool-extra/src/main/java/cn/hutool/extra/mail/MailAccount.java b/hutool-extra/src/main/java/cn/hutool/extra/mail/MailAccount.java
index b20dc9374..f5efacde3 100755
--- a/hutool-extra/src/main/java/cn/hutool/extra/mail/MailAccount.java
+++ b/hutool-extra/src/main/java/cn/hutool/extra/mail/MailAccount.java
@@ -23,8 +23,9 @@ public class MailAccount implements Serializable {
 	private static final String SMTP_HOST = "mail.smtp.host";
 	private static final String SMTP_PORT = "mail.smtp.port";
 	private static final String SMTP_AUTH = "mail.smtp.auth";
-	private static final String SMTP_CONNECTION_TIMEOUT = "mail.smtp.connectiontimeout";
 	private static final String SMTP_TIMEOUT = "mail.smtp.timeout";
+	private static final String SMTP_CONNECTION_TIMEOUT = "mail.smtp.connectiontimeout";
+	private static final String SMTP_WRITE_TIMEOUT = "mail.smtp.writetimeout";
 
 	// SSL
 	private static final String STARTTLS_ENABLE = "mail.smtp.starttls.enable";
@@ -117,11 +118,17 @@ public class MailAccount implements Serializable {
 	 * SMTP超时时长，单位毫秒，缺省值不超时
 	 */
 	private long timeout;
+
 	/**
 	 * Socket连接超时值，单位毫秒，缺省值不超时
 	 */
 	private long connectionTimeout;
 
+	/**
+	 * Socket写出超时值，单位毫秒，缺省值不超时
+	 */
+	private long writeTimeout;
+
 	/**
 	 * 自定义的其他属性，此自定义属性会覆盖默认属性
 	 */
@@ -518,6 +525,17 @@ public class MailAccount implements Serializable {
 		return this;
 	}
 
+	/**
+	 * 设置Socket写出超时值，单位毫秒，缺省值不超时
+	 *
+	 * @param writeTimeout Socket写出超时值，单位毫秒，缺省值不超时
+	 * @return this
+	 */
+	public MailAccount setWriteTimeout(final long writeTimeout) {
+		this.writeTimeout = writeTimeout;
+		return this;
+	}
+
 	/**
 	 * 获取自定义属性列表
 	 *
@@ -563,6 +581,10 @@ public class MailAccount implements Serializable {
 		if (this.connectionTimeout > 0) {
 			p.put(SMTP_CONNECTION_TIMEOUT, String.valueOf(this.connectionTimeout));
 		}
+		// issue#2355
+		if (this.writeTimeout > 0) {
+			p.put(SMTP_WRITE_TIMEOUT, String.valueOf(this.writeTimeout));
+		}
 
 		p.put(MAIL_DEBUG, String.valueOf(this.debug));
 
diff --git a/hutool-extra/src/test/resources/example/mail-example.setting b/hutool-extra/src/test/resources/example/mail-example.setting
index 0138ec4f2..94784ec03 100644
--- a/hutool-extra/src/test/resources/example/mail-example.setting
+++ b/hutool-extra/src/test/resources/example/mail-example.setting
@@ -37,4 +37,6 @@ splitlongparameters = false
 # SMTP超时时长，单位毫秒，缺省值不超时
 timeout = 0
 # Socket连接超时值，单位毫秒，缺省值不超时
-connectionTimeout = 0
\ No newline at end of file
+connectionTimeout = 0
+# Socket写出超时值，单位毫秒，缺省值不超时
+writeTimeout = 0