diff --git a/extension/js/common/browser/browser-msg.ts b/extension/js/common/browser/browser-msg.ts
index 4c566caa5c1..c72f4a0c937 100644
--- a/extension/js/common/browser/browser-msg.ts
+++ b/extension/js/common/browser/browser-msg.ts
@@ -20,6 +20,7 @@ import { Ui } from './ui.js';
 import { AuthRes } from '../api/authentication/generic/oauth.js';
 import { GlobalStore } from '../platform/store/global-store.js';
 import { BgUtils } from '../../service_worker/bgutils.js';
+import { ThunderbirdAttachment } from '../core/attachment.js';
 
 export type GoogleAuthWindowResult$result = 'Success' | 'Denied' | 'Error' | 'Closed';
 export type ScreenDimensions = { width: number; height: number; availLeft: number; availTop: number };
@@ -98,7 +99,7 @@ export namespace Bm {
   export type PgpBlockRetry = { frameId: string; messageSender: Dest };
   export type PgpBlockReady = { frameId: string; messageSender: Dest };
   export type ThunderbirdOpenPassphraseDialog = { acctEmail: string; longids: string };
-  export type ThunderbirdGetDownloadableAttachment = { attachment: messenger.messages.MessageAttachment };
+  export type ThunderbirdGetDownloadableAttachment = { attachments: messenger.messages.MessageAttachment[] };
   export type ThunderbirdInitiateAttachmentDownload = { decryptedFileName: string; decryptedContent: Buf };
 
   export namespace Res {
@@ -116,7 +117,7 @@ export namespace Bm {
     export type ExpirationCacheGet<V> = Promise<V | undefined>;
     export type ExpirationCacheSet = Promise<void>;
     export type ExpirationCacheDeleteExpired = Promise<void>;
-    export type ThunderbirdGetDownloadableAttachment = Buf | undefined;
+    export type ThunderbirdGetDownloadableAttachment = ThunderbirdAttachment[];
     export type ThunderbirdGetCurrentUser = string | undefined;
     export type ThunderbirdMsgGet = { attachments: messenger.messages.MessageAttachment[]; messagePart: messenger.messages.MessagePart };
     export type ThunderbirdOpenPassphraseDialog = Promise<void>;
diff --git a/extension/js/common/core/attachment.ts b/extension/js/common/core/attachment.ts
index 25909141051..f907c2cfb92 100644
--- a/extension/js/common/core/attachment.ts
+++ b/extension/js/common/core/attachment.ts
@@ -29,6 +29,12 @@ export type AttachmentProperties = {
   contentDescription?: string;
   contentTransferEncoding?: ContentTransferEncoding;
 };
+export type ThunderbirdAttachment = {
+  name: string;
+  contentType: string;
+  data: Buf;
+  treatAs: Attachment$treatAs;
+};
 export type AttachmentMeta = (AttachmentId | { data: Uint8Array }) & AttachmentProperties;
 
 export type FcAttachmentLinkData = { name: string; type: string; size: number };
diff --git a/extension/js/content_scripts/webmail/thunderbird/thunderbird-element-replacer.ts b/extension/js/content_scripts/webmail/thunderbird/thunderbird-element-replacer.ts
index 4f134759145..2186c300f30 100644
--- a/extension/js/content_scripts/webmail/thunderbird/thunderbird-element-replacer.ts
+++ b/extension/js/content_scripts/webmail/thunderbird/thunderbird-element-replacer.ts
@@ -3,7 +3,7 @@
 'use strict';
 
 import { BrowserMsg } from '../../../common/browser/browser-msg.js';
-import { Attachment } from '../../../common/core/attachment.js';
+import { Attachment, ThunderbirdAttachment } from '../../../common/core/attachment.js';
 import { Buf } from '../../../common/core/buf.js';
 import { KeyUtil } from '../../../common/core/crypto/key.js';
 import { DecryptError, DecryptErrTypes, MsgUtil, VerifyRes } from '../../../common/core/crypto/pgp/msg-util.js';
@@ -44,11 +44,9 @@ export class ThunderbirdElementReplacer extends WebmailElementReplacer {
         await this.messageVerify(signerKeys);
       }
       if (emailBodyToParse && attachments.length) {
-        for (const attachment of attachments) {
-          const fcAttachment = await BrowserMsg.send.bg.await.thunderbirdGetDownloadableAttachment({ attachment });
-          if (fcAttachment) {
-            await this.attachmentUiRenderer(attachment.name, fcAttachment, signerKeys, emailBodyToParse);
-          }
+        const fcAttachments = await BrowserMsg.send.bg.await.thunderbirdGetDownloadableAttachment({ attachments });
+        for (const fcAttachment of fcAttachments) {
+          await this.attachmentUiRenderer(fcAttachment, signerKeys, emailBodyToParse);
         }
       }
     }
@@ -112,14 +110,17 @@ export class ThunderbirdElementReplacer extends WebmailElementReplacer {
     $('body').html(pgpBlock); // xss-sanitized
   };
 
-  private attachmentUiRenderer = async (attachmentName: string, fcAttachment: Buf, verificationPubs: string[], plaintext: string) => {
-    if (attachmentName.endsWith('.pgp')) {
-      const generatedPgpTemplate = this.generatePgpAttachmentTemplate(attachmentName, fcAttachment);
+  private attachmentUiRenderer = async (fcAttachment: ThunderbirdAttachment, verificationPubs: string[], plaintext: string) => {
+    if (fcAttachment.treatAs === 'encryptedFile') {
+      const generatedPgpTemplate = this.generatePgpAttachmentTemplate(fcAttachment.name, fcAttachment.data);
       $('.pgp_attachments_block').append(generatedPgpTemplate); // xss-sanitized
-    } else if (Attachment.encryptedMsgNames.some(a => attachmentName.includes(a)) && !this.emailBodyFromThunderbirdMail) {
-      await this.messageDecrypt(verificationPubs, fcAttachment);
-    } else if (attachmentName.endsWith('.asc')) {
-      const sigText = new TextDecoder('utf-8').decode(fcAttachment).trim();
+    } else if (
+      (fcAttachment.treatAs === 'encryptedMsg' || Attachment.encryptedMsgNames.some(a => fcAttachment.name.includes(a))) &&
+      !this.emailBodyFromThunderbirdMail
+    ) {
+      await this.messageDecrypt(verificationPubs, fcAttachment.data);
+    } else if (fcAttachment.treatAs === 'signature') {
+      const sigText = new TextDecoder('utf-8').decode(fcAttachment.data).trim();
       if (this.resemblesSignedMsg(sigText)) {
         await this.messageVerify(verificationPubs, { plaintext, sigText });
       }
diff --git a/extension/js/service_worker/bg-handlers.ts b/extension/js/service_worker/bg-handlers.ts
index d45a3570a9e..43cc782ad96 100644
--- a/extension/js/service_worker/bg-handlers.ts
+++ b/extension/js/service_worker/bg-handlers.ts
@@ -166,13 +166,32 @@ export class BgHandlers {
   public static thunderbirdGetDownloadableAttachment = async (
     r: Bm.ThunderbirdGetDownloadableAttachment
   ): Promise<Bm.Res.ThunderbirdGetDownloadableAttachment> => {
+    const processableAttachments: Bm.Res.ThunderbirdGetDownloadableAttachment = [];
     const [tab] = await messenger.mailTabs.query({ active: true, currentWindow: true });
     if (tab.id) {
-      const rawAttachment = await messenger.messages.getAttachmentFile(tab.id, r.attachment.partName);
-      const data = new Uint8Array(await rawAttachment.arrayBuffer());
-      return new Attachment({ data }).getData();
+      const fcAttachments: Attachment[] = [];
+      // convert Thunderbird Attachments to FlowCrypt recognizable Attachments
+      for (const tbAttachment of r.attachments) {
+        const rawAttachment = await messenger.messages.getAttachmentFile(tab.id, tbAttachment.partName);
+        fcAttachments.push(
+          new Attachment({
+            data: new Uint8Array(await rawAttachment.arrayBuffer()),
+            type: tbAttachment.contentType,
+            name: tbAttachment.name,
+            length: tbAttachment.size,
+          })
+        );
+      }
+      for (const fcAttachment of fcAttachments) {
+        processableAttachments.push({
+          name: fcAttachment.name,
+          contentType: fcAttachment.type,
+          data: fcAttachment.getData(),
+          treatAs: fcAttachment.treatAs(fcAttachments),
+        });
+      }
     }
-    return;
+    return processableAttachments;
   };
 
   public static thunderbirdInitiateAttachmentDownload = async (