Mails invalid signature because of encoding of periods in quoted printable [migrated]
I‘m sending a mail encoded with quoted printable encoding that contains some dots .. There is a problem with a specific mailserver/customer. For some reason, they receive the mail in such a form that each dot is encoded as =2E ultimately breaking the signature.
What system could possibly do this? It‘s not defined in the standard to encode dots as well. What would be the best practice solution? Encode every dot to prevent the system from converting? Did anybody of you encounter this problem already?
I'm sending the mails via python using the email package. The quoted-printable encoding will happen using the set_content method in python3. The problem only occurs for a special mail server. Here is an example email:
Mail after leaving my program:
Content-Type: text/html; charset="utf-8"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
<!DOCTYPE html><html><h1>Test Email</h1><p>This is a test email. Showing En=
coding of points in quoted-printable.</p></html>
Test mail received by the mail client:
Content-Type: text/html; charset="utf-8"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
<!DOCTYPE html><html><h1>Test Email</h1><p>This is a test email=2E Showing =
Encoding of points in quoted-printable=2E</p></html>
