HTML PDF Encrypted e-mail

Gateway
1

Hi,

I was wondering if it's possible to send HTML encoded PDF encrypted e-mail. I noticed that embedded images in the e-mail do not show up. Is this an issue with the PDF viewer or ciphermail not processing HTML e-mail? Is it a security issue?

Thanks in advance

attachment.htm (2.15 KB)

2

Does anyone have any ideas?

Thanks

attachment.htm (3.09 KB)

···

From: Dino Edwards via Users <users(a)lists.ciphermail.com>
Sent: Monday, June 7, 2021 9:17 PM
To: users(a)lists.ciphermail.com
Cc: Dino Edwards <dino.edwards(a)mydirectmail.net>
Subject: HTML PDF Encrypted e-mail

Hi,

I was wondering if it's possible to send HTML encoded PDF encrypted e-mail. I noticed that embedded images in the e-mail do not show up. Is this an issue with the PDF viewer or ciphermail not processing HTML e-mail? Is it a security issue?

Thanks in advance

3

HTML email is not supported because converting HTML to a PDF is not
trivial. If an email only contains an HTML, the HTML part is converted
to a text email (not trivial but easier).

Whether or not an attached image gets added depends on the MIME
structure. With images added as attachments and an HTML alternative
part, the MIME structure with most email clients looks like:

multipart
  alternative part
    text part
    html part
  
  image1
  image2
  ...

If any images are only considered to be used for HTML it might look
like

multipart
  alternative part
    text part
    html part
      image1
      image2
      ...

Apple Mail might even complicates things.

For example with most email clients, attaching a PDF looks like

multipart
  alternative part
    text part
    html part
  
  pdf1
  pdf2

...

Apple Mail however sometimes adds the PDFs inline with the HTML part

multipart
  alternative part
    text part
    html part
      pdf1
      pdf2
      ...

The scanner which scans the email for parts, searches for the text part
and if found, will stop scanning the alternative part. Any inline
images or attachments under the HTML part (for example inline images or
Apple Mail inline attachment) will therefore not be added as
attachments because they are considered to be only valid for HTML.

However, if you enable "Deep scan", the gateway will continue scanning
the HTML alternative part for attachments

https://www.ciphermail.com/documentation/gateway-administration-guide/settings.html#deep-scan-sender-p

Any inline image will then also be added.

Kind regards,

Martijn Brinkers

···

--
CipherMail email encryption
Email encryption with support for S/MIME,
OpenPGP, PDF Messenger and Webmail Messenger

On Fri, 2021-06-11 at 12:34 +0000, Dino Edwards via Users wrote:

Does anyone have any ideas?

Thanks

From: Dino Edwards via Users <users(a)lists.ciphermail.com>
Sent: Monday, June 7, 2021 9:17 PM
To: users(a)lists.ciphermail.com
Cc: Dino Edwards <dino.edwards(a)mydirectmail.net>
Subject: HTML PDF Encrypted e-mail

Hi,

I was wondering if it’s possible to send HTML encoded PDF encrypted
e-mail. I noticed that embedded images in the e-mail do not show up.
Is this an issue with the PDF viewer or ciphermail not processing
HTML e-mail? Is it a security issue?

Thanks in advance

4

Thank you Martijn!

···

-----Original Message-----
From: Martijn Brinkers <martijn(a)ciphermail.com>
Sent: Friday, June 11, 2021 8:47 AM
To: users(a)lists.ciphermail.com
Cc: Dino Edwards <dino.edwards(a)mydirectmail.net>
Subject: Re: Re: HTML PDF Encrypted e-mail

HTML email is not supported because converting HTML to a PDF is not trivial. If an email only contains an HTML, the HTML part is converted to a text email (not trivial but easier).

Whether or not an attached image gets added depends on the MIME structure. With images added as attachments and an HTML alternative part, the MIME structure with most email clients looks like:

multipart
  alternative part
    text part
    html part
  
  image1
  image2
  ...

If any images are only considered to be used for HTML it might look like

multipart
  alternative part
    text part
    html part
      image1
      image2
      ...

Apple Mail might even complicates things.

For example with most email clients, attaching a PDF looks like

multipart
  alternative part
    text part
    html part
  
  pdf1
  pdf2

...

Apple Mail however sometimes adds the PDFs inline with the HTML part

multipart
  alternative part
    text part
    html part
      pdf1
      pdf2
      ...

The scanner which scans the email for parts, searches for the text part and if found, will stop scanning the alternative part. Any inline images or attachments under the HTML part (for example inline images or Apple Mail inline attachment) will therefore not be added as attachments because they are considered to be only valid for HTML.

However, if you enable "Deep scan", the gateway will continue scanning the HTML alternative part for attachments

https://www.ciphermail.com/documentation/gateway-administration-guide/settings.html#deep-scan-sender-p

Any inline image will then also be added.

Kind regards,

Martijn Brinkers

--
CipherMail email encryption
Email encryption with support for S/MIME, OpenPGP, PDF Messenger and Webmail Messenger

On Fri, 2021-06-11 at 12:34 +0000, Dino Edwards via Users wrote:

Does anyone have any ideas?

Thanks

From: Dino Edwards via Users <users(a)lists.ciphermail.com>
Sent: Monday, June 7, 2021 9:17 PM
To: users(a)lists.ciphermail.com
Cc: Dino Edwards <dino.edwards(a)mydirectmail.net>
Subject: HTML PDF Encrypted e-mail

Hi,

I was wondering if it’s possible to send HTML encoded PDF encrypted
e-mail. I noticed that embedded images in the e-mail do not show up.
Is this an issue with the PDF viewer or ciphermail not processing HTML
e-mail? Is it a security issue?

Thanks in advance