flutter/lib/features/mail/domain/compose_draft_body.dart

@@ -267,7 +267,7 @@ List<String>? _plainParagraphLines(dom.Element paragraph) {
   final List<String> lines = <String>[];
   for (final dom.Node child in paragraph.nodes) {
     if (child is dom.Text) {
-      current.write(child.data.replaceAll(' ', ' '));
+      current.write(child.data.replaceAll('\u00A0', ' '));
     } else if (child is dom.Element && child.localName == 'br') {
       lines.add(current.toString());
       current.clear();
@@ -381,7 +381,7 @@ ComposeQuote composeQuoteOf(dom.Element blockquote, {required bool keepHtml}) {
 List<String> _cellsOf(dom.Element row) => <String>[
   for (final dom.Element cell in row.children)
     if (cell.localName == 'td' || cell.localName == 'th')
-      nodeTextOf(cell).replaceAll(' ', ' ').trim(),
+      nodeTextOf(cell).replaceAll('\u00A0', ' ').trim(),
 ];
 
 /// 보낸 사람 머리 줄의 이름 — `이도윤 <doyun@…>` → "이도윤" (이름이 없으면 주소)

flutter/test/features/mail/compose_rules_test.dart

@@ -16,7 +16,7 @@ import 'package:flutter_test/flutter_test.dart';
 
 import '../../support/mail_fakes.dart';
 
-const String _nbsp = ' ';
+const String _nbsp = '\u00A0';
 const String _wrapper =
     '<div style="font-family: \'Malgun Gothic\', \'맑은 고딕\', \'Apple SD Gothic Neo\', sans-serif; font-size: 14px; line-height: 1.75">';
 const String _p = '<p style="margin: 0">';

flutter/test/features/mail/mail_reader_rules_test.dart

@@ -156,7 +156,7 @@ void main() {
       expect(safeFileName(r'a\b:c*d?e"f<g>h|i.txt'), 'a_b_c_d_e_f_g_h_i.txt');
       expect(safeFileName('보고\u0000서\u001F.pdf'), '보고서.pdf');
       expect(safeFileName('invoice\u202Efdp.exe'), 'invoicefdp.exe');
-      expect(safeFileName('​견적.xlsx'), '견적.xlsx');
+      expect(safeFileName('\u200B\uFEFF견적.xlsx'), '견적.xlsx');
     });
 
     test('앞뒤 공백 · 점을 지우고, 비면 기본 이름', () {