Add java.time support to MimeMessageHelper

spring-context-support/src/main/java/org/springframework/mail/MailMessage.java

@@ -16,6 +16,7 @@
 
 package org.springframework.mail;
 
+import java.time.Instant;
 import java.util.Date;
 
 /**
@@ -53,6 +54,16 @@ public interface MailMessage {
 
 	void setSentDate(Date sentDate) throws MailParseException;
 
+	/**
+	 * Set the sent-date of the message.
+	 * @param sentDate the date to set (never {@code null})
+	 * @throws MailParseException in case of errors
+	 * @since 7.1
+	 */
+	default void setSentDate(Instant sentDate) throws MailParseException {
+		setSentDate(Date.from(sentDate));
+	}
+
 	void setSubject(String subject) throws MailParseException;
 
 	void setText(String text) throws MailParseException;

spring-context-support/src/main/java/org/springframework/mail/javamail/MimeMailMessage.java

@@ -16,6 +16,7 @@
 
 package org.springframework.mail.javamail;
 
+import java.time.Instant;
 import java.util.Date;
 
 import jakarta.mail.MessagingException;
@@ -163,6 +164,16 @@ public void setSentDate(Date sentDate) throws MailParseException {
 		}
 	}
 
+	@Override
+	public void setSentDate(Instant sentDate) throws MailParseException {
+		try {
+			this.helper.setSentDate(sentDate);
+		}
+		catch (MessagingException ex) {
+			throw new MailParseException(ex);
+		}
+	}
+
 	@Override
 	public void setSubject(String subject) throws MailParseException {
 		try {

spring-context-support/src/main/java/org/springframework/mail/javamail/MimeMessageHelper.java

@@ -21,6 +21,7 @@
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.UnsupportedEncodingException;
+import java.time.Instant;
 import java.util.Date;
 
 import jakarta.activation.DataHandler;
@@ -763,6 +764,17 @@ public void setSentDate(Date sentDate) throws MessagingException {
 		this.mimeMessage.setSentDate(sentDate);
 	}
 
+	/**
+	 * Set the sent-date of the message.
+	 * @param sentDate the date to set (never {@code null})
+	 * @throws MessagingException in case of errors
+	 * @since 7.1
+	 */
+	public void setSentDate(Instant sentDate) throws MessagingException {
+		Assert.notNull(sentDate, "Sent date must not be null");
+		this.mimeMessage.setSentDate(Date.from(sentDate));
+	}
+
 	/**
 	 * Set the subject of the message, using the correct encoding.
 	 * @param subject the subject text

spring-context-support/src/test/java/org/springframework/mail/javamail/JavaMailSenderTests.java

@@ -21,6 +21,7 @@
 import java.util.Calendar;
 import java.util.Date;
 import java.util.GregorianCalendar;
+import java.time.Instant;
 import java.util.List;
 import java.util.Properties;
 import java.util.stream.Stream;
@@ -452,6 +453,28 @@ void connectionWithFailure() {
 		assertThatExceptionOfType(MessagingException.class).isThrownBy(sender::testConnection);
 	}
 
+	@Test
+	void javaTimeSentDateSupport() throws Exception {
+		Instant sentDate = Instant.parse("2026-06-20T10:15:30.00Z");
+		Date expectedDate = Date.from(sentDate);
+
+		// Test MimeMessageHelper
+		MimeMessage mimeMessage = sender.createMimeMessage();
+		MimeMessageHelper helper = new MimeMessageHelper(mimeMessage);
+		helper.setSentDate(sentDate);
+		assertThat(mimeMessage.getSentDate()).isEqualTo(expectedDate);
+
+		// Test MimeMailMessage
+		MimeMailMessage mimeMailMessage = new MimeMailMessage(helper);
+		mimeMailMessage.setSentDate(sentDate);
+		assertThat(mimeMessage.getSentDate()).isEqualTo(expectedDate);
+
+		// Test SimpleMailMessage (via MailMessage interface default method)
+		SimpleMailMessage simpleMailMessage = new SimpleMailMessage();
+		simpleMailMessage.setSentDate(sentDate);
+		assertThat(simpleMailMessage.getSentDate()).isEqualTo(expectedDate);
+	}
+
 
 	private static Stream<String> addresses(Address[] addresses) {
 		return Arrays.stream(addresses).map(InternetAddress.class::cast).map(InternetAddress::getAddress);