diff --git a/public/index.html b/public/index.html
index b491319..708ba38 100644
--- a/public/index.html
+++ b/public/index.html
@@ -1806,9 +1806,9 @@
                     const fields = {};
 
                     // add file attachments
+                    var fileAttachmentsTotalSize = 0;
                     if(this.newMessageFiles.length > 0){
                         const fileAttachments = [];
-                        var fileAttachmentsTotalSize = 0;
                         for(const file of this.newMessageFiles){
                             fileAttachmentsTotalSize += file.size;
                             fileAttachments.push({
@@ -1820,7 +1820,9 @@
                     }
 
                     // add image attachment
+                    var imageTotalSize = 0;
                     if(this.newMessageImage){
+                        imageTotalSize = this.newMessageImage.size;
                         fields["image"] = {
                             // Reticulum sends image type as "jpg" or "png" and not "image/jpg" or "image/png"
                             "image_type": this.newMessageImage.type.replace("image/", ""),
@@ -1829,13 +1831,26 @@
                     }
 
                     // add audio attachment
+                    var audioTotalSize = 0;
                     if(this.newMessageAudio){
+                        audioTotalSize = this.newMessageImage.size;
                         fields["audio"] = {
                             "audio_mode": this.newMessageAudio.audio_mode,
                             "audio_bytes": this.arrayBufferToBase64(await this.newMessageAudio.audio_blob.arrayBuffer()),
                         };
                     }
 
+                    // calculate estimated message size in bytes
+                    const contentSize = this.newMessageText.length;
+                    const totalMessageSize = contentSize + fileAttachmentsTotalSize + imageTotalSize + audioTotalSize;
+
+                    // ask user if they still want to send message if it may be rejected by sender
+                    if(totalMessageSize > 1000 * 900){ // actual limit in LXMF Router is 1mb
+                        if(!confirm(`Your message exceeds 900KB (It's ${this.formatBytes(totalMessageSize)}). It may be rejected by the recipient unless they have increased their delivery limit. Do you want to try sending anyway?`)){
+                            return;
+                        }
+                    }
+
                     // send message to reticulum
                     const response = await window.axios.post(`/api/v1/lxmf-messages/send`, {
                         "lxmf_message": {