How to add a link to an attached file inside an email?

Question

HTML

You need to add a link to download the attached zip archive inside the html email. Relative path "in the same folder" does not work. Is it even possible?

Answer 1

For emails, a link to an attached or inline file is made via the URI cid:, cid: contains the value of the Content-ID header of the part of the email containing the attachment. for example

From: ...
Subject: test
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="123"

--123
Content-Type: text/html; charset=utf-8
...
<a href="cid:[email protected]">attached file</a>
...
--123
Content-Type: application/zip
Content-Transfer-Encoding: base64
Content-Disposition: attachment
Content-ID: <[email protected]>

....
--123--

But I would strongly not recommend doing this, because how it will work in email clients / web services is not known.