Split address header's value into multiple lines if too long

lib/src/smtp/internal_representation/ir_header.dart

@@ -37,13 +37,23 @@ abstract class _IRHeader extends _IROutput {
  yield convert.utf8.encode(_name);
  yield _$colonSpace;
 
- bool second = false;
+ var len = 2, //2 = _$commaSpace
+ second = false;
  for (final address in addresses) {
- if (second) yield _$commaSpace;
- else second = true;
-
  final name = address.sanitizedName,
  maddr = address.sanitizedAddress;
+ var adrlen = maddr.length;
+ if (name != null) adrlen += name.length + 3; //not accurate but good enough
+
+ if (second) {
+ yield _$commaSpace;
+
+ if (len + adrlen > maxEncodedLength) {
+ len = 2;
+ yield _$eolSpace;
+ }
+ } else second = true;
+
  if (name == null) {
  yield convert.utf8.encode(maddr);
  } else {
@@ -54,6 +64,8 @@ abstract class _IRHeader extends _IROutput {
  yield convert.utf8.encode(maddr);
  yield _$gt;
  }
+
+ len += adrlen;
  }
 
  yield _$eol;