>From a brief look at mailman source (src/mailman/handlers/decorate.py if
anyone is interested), seems it will always mangle the original message
body when it is a single-part text/plain.
So sending as base64 does not help since mailman will recode it, as can
be seen from the test emails I just
---
sent as base64
testfile | 3 +++
1 file changed, 3 insertions(+)
create mode 100644 testfile
diff --git a/testfile b/testfile
new file mode 100644
index 00..68bb7cbf9c
--- /dev/null
+++ b/testfile
@@ -0,0 +1,3 @@
+This is a test file with very long lines
---
sent as quoted-printable
testfile | 3 +++
1 file changed, 3 insertions(+)
create mode 100644 testfile
diff --git a/testfile b/testfile
new file mode 100644
index 00..68bb7cbf9c
--- /dev/null
+++ b/testfile
@@ -0,0 +1,3 @@
+This is a test file with very long lines
