Hello Monks,

My time in the forest alone writing poetry about nature has been long, but a curious question has crossed my path, and I find myself again in this bustling city.

A user of mine is sending emails that are received with broken URLs. Dots are removed. I suspect a broken sendmail implementation, that's not doing its job dot stuffing, when it finds a dot as the first character of a line, for example: 

 
#!/usr/bin/perl 

use MIME::Entity; 

my $str = 'filler text to get the first char of line 2 to be a dot____
+__ http://google.com'; 

print MIME::Entity->build(
    Data     => $str, 
    Type     => 'text/plain',
    Encoding => 'quoted-printable',
)->as_string;

[download]
Returns, 
 
Content-Type: text/plain
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-Mailer: MIME-tools 5.505 (Entity 5.505)

filler text to get the first char of line 2 to be a dot______ http://g
+oogle=
.com=

[download]

To me, this seems correct.

One option for me as the app owner is to do this dot stuffing myself, which I am very much against, as I feel it's a hack to a broken system upstream. And I'll probably do it wrong - or at least do it badly. I'll have users now with broken links - but only because there's now too many dots!

Another option is to encode this myself so, "." turns into, "=2E". But, I don't see any way to do this through the tool chain. Looking at the docs for MIME::QuotedPrint, there is no option to encode dots, nor are there any similar options in MIME::Entity, nor is the issue brought up in Net::SMTP. This makes me think that all the authors of all these modules in the tool chain understand this problem better than I, and there was a concerted effort to not do this, "newline starts with a dot encoding".

The only thing similar to this that I have found is that lines that only have a single dot are encoded, stopping the SMTP server from truncating a message, like so: 

 
perl -MMIME::Entity -e 'print MIME::Entity->build(Encoding => "quoted-
+printable", Data     => "some text\n.\nmore text")->as_string;'

[download]

prints, 

 

Content-Type: text/plain
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-Mailer: MIME-tools 5.505 (Entity 5.505)

some text
=2E
more text=

[download]

So, am I missing something obvious? are there solutions that anyone else has come to, to appease broken SMTP clients without needing to post filtering output from MIME::Entity?

-skazat

In reply to Double Dot Stuffing by skazat

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