Coding email signatures

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SirHumphreyAppleby

2852 posts

Uber Geek

#2302427 20-Aug-2019 16:22

arcon:

Yep as mentioned this was with an HMTL sig (Thunderbird), so the file prefix does work to a remote gmail account on android. But my test logo (only 350 bytes) done this way loads noticeably slower than a sig remotely stored on wix. That alone is enough to turn me off attachments :/

It does work? If so, Thunderbird will be converting it to either cid: or data:, because file: will not work.

If using cid:, both further MIME processing and base64 decoding will be required. If data:, just base64 decoding will be required. Unlike a further HTTP request which can occur while parsing the page, these may not (or in many cases cannot) be done until after the HTML and other attachments are fully parsed.

arcon

423 posts

Ultimate Geek

#2302428 20-Aug-2019 16:29

Shindig:

I use external links stored on Azure blob storage, with a CDN distributing them around the world. In my experience HTML signatures are a massive drain of time, as people have mentioned previously; to get rendered correctly.

Mine's a fairly basic sig & I was able to get a consistent render on Apple, Android & desktop with Thunderbird & Outlook Live. I don't have access to older clients, are there any widely used that are likely to cause problems? gmail was the most finicky but nothing that couldn't be fixed.

SirHumphreyAppleby

2852 posts

Uber Geek

#2302437 20-Aug-2019 16:51

@arcon. I have tested this for you. When given an img src specified as a file:, Thunderbird converts this to an inline attachment and references it with the Content-ID. The image cannot be rendered until after it has been found (later) in the MIME structure and base64 decoded. Depending on the speed of the client (CPU, I/O performance etc.), this may be slower than simply requesting a copy from a remote source, which is delivered as usable binary data, and can be obtained while the HTML is still being parsed.

This is a multi-part message in MIME format.
--------------2E2853B97BEA874D4147F628
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit

--
Hello

--------------2E2853B97BEA874D4147F628
Content-Type: multipart/related;
boundary="------------8591D76BE4D48FBBA8E1D4C2"

--------------8591D76BE4D48FBBA8E1D4C2
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: 7bit

<html>
<head>

<meta http-equiv="content-type" content="text/html; charset=UTF-8">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<p><br>
</p>
<div class="moz-signature">-- <br>
<img src="cid:part1.F158028B.4C3513D8@anonymous.net.nz" alt="Hello"></div>
</body>
</html>

--------------8591D76BE4D48FBBA8E1D4C2
Content-Type: image/png;
name="Invite.png"
Content-Transfer-Encoding: base64
Content-ID: <part1.F158028B.4C3513D8@anonymous.net.nz>
Content-Disposition: inline;
filename="Invite.png"

iVBORw0KGgoAAAANSUhEUgAAATwAAADZCAIAAAAymRvUAAAAAXNSR0IArs4c6QAAAARnQU1B
...

--------------8591D76BE4D48FBBA8E1D4C2--

--------------2E2853B97BEA874D4147F628--

arcon

423 posts

Ultimate Geek

#2302563 20-Aug-2019 18:43

SirHumphreyAppleby:

@arcon. I have tested this for you. When given an img src specified as a file:, Thunderbird converts this to an inline attachment and references it with the Content-ID. The image cannot be rendered until after it has been found (later) in the MIME structure and base64 decoded. Depending on the speed of the client (CPU, I/O performance etc.), this may be slower than simply requesting a copy from a remote source, which is delivered as

Interesting, seems to verify what I found, it was 2 seconds slower than remote links when viewed on my S9 which I wouldn't have thought was a slouch lol.

BlakJak

1276 posts

Uber Geek

Trusted

#2305311 24-Aug-2019 15:31

I found that embedding the image into the email being sent, adds an attachment to every email (so then hard to sort by emails with file attachment when every email has a file attachment!) and makes every email bigger (storage wasted).

Host on a website and reference using HTML. Most organisations will have a website somewhere that can enable this easily.

No signature to see here, move along...

SirHumphreyAppleby

2852 posts

Uber Geek

#2305360 24-Aug-2019 15:53

BlakJak: I found that embedding the image into the email being sent, adds an attachment to every email (so then hard to sort by emails with file attachment when every email has a file attachment!)

Content-Dispositon: Inline; will usually stop these files showing as attachments, but it is client dependent. The method Thunderbird is using, with nested MIME containers, is the most reliable way I've found to get the images to display and not show up as attachments. It would be nice to be able to do both - have an attachment which is also referenced in HTML, but that doesn't work reliably with many clients.

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