diff --git a/app/src/main/java/com/sun/mail/smtp/SMTPTransport.java b/app/src/main/java/com/sun/mail/smtp/SMTPTransport.java
index 1219c289b4..826a88189a 100644
--- a/app/src/main/java/com/sun/mail/smtp/SMTPTransport.java
+++ b/app/src/main/java/com/sun/mail/smtp/SMTPTransport.java
@@ -16,6 +16,7 @@
 
 package com.sun.mail.smtp;
 
+import android.os.ParcelFileDescriptor;
 import android.text.TextUtils;
 
 import java.io.*;
@@ -1300,6 +1301,7 @@ public class SMTPTransport extends Transport {
 	try {
 	    mailFrom();
 	    rcptTo();
+
 	    eu.faircode.email.ObjectHolder<Integer> total = new eu.faircode.email.ObjectHolder<>();
 	    total.value = 0;
 	    this.message.writeTo(new OutputStream(){
@@ -1308,10 +1310,37 @@ public class SMTPTransport extends Transport {
 				total.value++;
 			}
 		});
+
+	    Integer _fd = null;
+	    try {
+			_fd = ParcelFileDescriptor.fromSocket(serverSocket).getFd();
+		} catch (Throwable ex) {
+			eu.faircode.email.Log.w(ex);
+		}
+	    final Integer fd = _fd;
+
 	    TraceOutputStream.IReport reporter =
 			(TraceOutputStream.IReport) session.getProperties()
 				.get("mail." + name + ".reporter");
-	    traceOutput.setReporter(total.value, reporter);
+	    traceOutput.setReporter(total.value, new TraceOutputStream.IReport() {
+			@Override
+			public void report(int pos, int total) {
+				if (reporter == null)
+					return;
+
+				int q = 0;
+				if (fd != null)
+					q = eu.faircode.email.ConnectionHelper.jni_socket_get_send_buffer(fd);
+				if (q > pos)
+					q = pos;
+
+				int sent = pos - q;
+				if (sent > total)
+					sent = total;
+
+				reporter.report(sent, total);
+			}
+		});
 	    if (chunkSize > 0 && supportsExtension("CHUNKING")) {
 		/*
 		 * Use BDAT to send the data in chunks.
diff --git a/app/src/main/java/eu/faircode/email/ConnectionHelper.java b/app/src/main/java/eu/faircode/email/ConnectionHelper.java
index 713a0537c7..9596428540 100644
--- a/app/src/main/java/eu/faircode/email/ConnectionHelper.java
+++ b/app/src/main/java/eu/faircode/email/ConnectionHelper.java
@@ -89,6 +89,8 @@ public class ConnectionHelper {
 
     public static native int jni_socket_keep_alive(int fd, int seconds);
 
+    public static native int jni_socket_get_send_buffer(int fd);
+
     static class NetworkState {
         private Boolean connected = null;
         private Boolean suitable = null;
diff --git a/app/src/main/jni/fairemail.cc b/app/src/main/jni/fairemail.cc
index ca7c982fe6..330452584d 100644
--- a/app/src/main/jni/fairemail.cc
+++ b/app/src/main/jni/fairemail.cc
@@ -5,6 +5,7 @@
 #include <errno.h>
 #include <sys/socket.h>
 #include <netinet/tcp.h>
+#include <sys/ioctl.h>
 
 #include "compact_enc_det/compact_enc_det.h"
 #include "cld_3/src/nnet_language_identifier.h"
@@ -140,3 +141,15 @@ Java_eu_faircode_email_ConnectionHelper_jni_1socket_1keep_1alive(
 
     return res;
 }
+
+extern "C"
+JNIEXPORT jint JNICALL
+Java_eu_faircode_email_ConnectionHelper_jni_1socket_1get_1send_1buffer(
+        JNIEnv *env, jclass clazz,
+        jint fd) {
+    int queued = 0;
+    int res = ioctl(fd, TIOCOUTQ, &queued);
+    if (res != 0)
+        log_android(ANDROID_LOG_DEBUG, "ioctl(TIOCOUTQ) res=%d queued=%d", res, queued);
+    return (res == 0 ? queued : 0);
+}
\ No newline at end of file