System.Net.Mail creating invalid emails and eml files? Inserting extra dots in host names

Question

It appears that .NET\'s SmtpClient is creating emails with an extra dot in host names if the dot was to appear at the beginning of a MIME encoded line (e.g. test.com sometim

Answer 1

In .Net 2.0

X-Sender: test@test.com
X-Receiver: Test@test.com
MIME-Version: 1.0
From: test@test.com
To: Test@test.com
Date: 6 Jul 2011 21:29:04 +0100
Subject: Test
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: quoted-printable

Hello this is  a short test of the issue: https://test.com/:=

It looks like it is wrapping the text at a certain character length per line. I vaguely remember there was an issue in .Net 2.0 where by default it doesn't do this which can cause problems with spam filters.

In fact increasing the size of the message gives the following in .Net 4.0:

X-Sender: test@test.com
X-Receiver: Test@test.com
MIME-Version: 1.0
From: test@test.com
To: Test@test.com
Date: 6 Jul 2011 21:34:21 +0100
Subject: Test
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: quoted-printable

Hello this is  a short test of the sssssssssssssssssissue: https://test.com/:=20

Seems like a bug.

A workaround might be to change the BodyEncoding to something other than ASCII.