diff --git a/app/plugins/builtins/mail/services.py b/app/plugins/builtins/mail/services.py
index 79f476a..27873b8 100644
--- a/app/plugins/builtins/mail/services.py
+++ b/app/plugins/builtins/mail/services.py
@@ -772,13 +772,19 @@ async def imap_sync_account(
                             if existing_att_count == 0:
                                 for att_data in attachments:
                                     try:
+                                        raw_filename = att_data["filename"] or "attachment"
+                                        try:
+                                            from email.header import decode_header, make_header
+                                            decoded_filename = str(make_header(decode_header(raw_filename)))
+                                        except Exception:
+                                            decoded_filename = raw_filename
                                         storage_path = await _save_attachment_to_storage(
-                                            existing_mail.id, att_data["filename"], att_data["content"]
+                                            existing_mail.id, decoded_filename, att_data["content"]
                                         )
                                         attachment = MailAttachment(
                                             tenant_id=tenant_id,
                                             mail_id=existing_mail.id,
-                                            filename=_sanitize_filename(att_data["filename"]),
+                                            filename=_sanitize_filename(decoded_filename),
                                             mime_type=att_data["mime_type"],
                                             size_bytes=att_data["size"],
                                             storage_path=storage_path,
@@ -823,13 +829,20 @@ async def imap_sync_account(
                     # Save attachments to storage and DB
                     for att_data in attachments:
                         try:
+                            # Decode MIME-encoded filenames (e.g. =?utf-8?q?...?=)
+                            raw_filename = att_data["filename"] or "attachment"
+                            try:
+                                from email.header import decode_header, make_header
+                                decoded_filename = str(make_header(decode_header(raw_filename)))
+                            except Exception:
+                                decoded_filename = raw_filename
                             storage_path = await _save_attachment_to_storage(
-                                mail.id, att_data["filename"], att_data["content"]
+                                mail.id, decoded_filename, att_data["content"]
                             )
                             attachment = MailAttachment(
                                 tenant_id=tenant_id,
                                 mail_id=mail.id,
-                                filename=_sanitize_filename(att_data["filename"]),
+                                filename=_sanitize_filename(decoded_filename),
                                 mime_type=att_data["mime_type"],
                                 size_bytes=att_data["size"],
                                 storage_path=storage_path,