Q: How can I create an email which shows external images?

Include a link in the email to the page containing the image.

I'll assume you were looking to do a "fancy" HTML-format mail message, and to pull in the image into the display in-line within the receiver's mail client, rather than attaching the message or requiring the user to click on a link...  If so...

Mail.app lacks generic HTML-editing capabilities.

Create an HTML file containing your message and embedded links or whatever else using your preferred tools, open the HTML file using Safari, and select to Share the file by mailing it from within Safari. 

Expect that more than a few of recipients will block remote image loads (as big images can consume wireless data, the image loads track users, etc), so make sure you account for your image being blocked in your formatting and likely include some alt tags, etc.  Also format the HTML generically and test it, as different mail clients will display HTML differently.

As an alternative to the above, here's a longstanding and seldom-used Stationery mechanism in Mail.app that you might want to look at.   Open

Mail.app help and search for Stationery for details on that.

If my assumptions above are incorrect and you seek to send somebody a link to the file — rather than rendering the image in-line within the HTML message — then definitely do as  BobTheFisherman quite correctly suggests, and embed the link in the message.

coxorange wrote:

 

Thanks for your answer!

MrHoffman wrote:

I'll assume you were looking to do a "fancy" HTML-format mail message, and to pull in the image into the display in-line within the receiver's mail client, rather than attaching the message or requiring the user to click on a link...  If so...

You're right, but nothing fancy. I just want to send external photos which instantly appear in the emails when opened.

(The reason for this: I keep copies of my sent emails and don't want to waste space with copies of the large photos too.)

Might want to ponder using a tool or an approach other than Mail.app for photo distributions and posting.  Mail.app isn't the best tool for this.  If you're running a web site, there are packages which can present and maintain photo galleries.

I have some small galleries in Drupal, which can be extended to provide this — folks can look at the photo galleries themselves.  The ownCloud package is another option, if you're running your own server or slice somewhere, and it's quite capable of a number of useful tasks.  There are other packages ranging from email tools that can edit HTML to web content management systems with galleries, to full-on cloud packages.

Or there are undoubtedly public photo sharing sites that can be configured for some privacy, not that I've looked into any of those.

Or you can use Dropbox or your own server to host your data, as you're currently doing.  (Authentication and access controls can be an issue with rolling your own, as Googlebot and the other spiders are good at finding content.  "Private" URLs tend to leak out, and it wouldn't surprise me that Google would find those URLs via gmail recipients, if not elsewhere.  But that's fodder for another discussion or two.)

Create an HTML file containing your message and embedded links or whatever else using your preferred tools, open the HTML file using Safari, and select to Share the file by mailing it from within Safari.

Would this also work with copy/paste? (from the HTML editor into Mail)

You'd need to paste raw into the message buffer and AFAIK Mail.app does not offer that.  I'd have suggested it, otherwise.

As an alternative to the above, here's a longstanding and seldom-used Stationery mechanism in Mail.app that you might want to look at.   Open Mail.app help and search for Stationery for details on that.

In Mail help I found only "Personalize messages with stationery", but I can't find information about how to include own external images.

How can I use Stationery to do this?

It's HTML.  Customize an existing template or create your own stationary, and populate it with the HTML that's necessary here.  I don't have pointers to the customized-stationery descriptions around the 'net, but I know those exist.

I know you marked the issue solved but I feel it necessary to point out that regardless what you do to "fancy" up your emails, it is totally in control of the recipient how that fancy email is displayed.

So don't spend a lot of time and money on this. Most people don't allow HTML and embedded images to display in email, for good reason. You may have noticed how much advertising and spam you get in email. Allowing HTML and images allows the advertisers/spammers to embed links and malicious code which if acted on by the recipient can lead to malware etc. Images in email can also contain web bugs.

So most people disable "fancy" email reading.

Seems that this behavior has changed in OS X.   Shipping out these messages will require a different mail client here, or the use a mail client library to send these messages, or some other approach to distributing these HTML messages with what amounts to a web beacon; a web tracker.  Having run various tests with Safari and Mail on the current Yosemite, it's all attachments or Mail Drop.

My experience with SMTP mail and MIME-encoding leads me to use other tools for file distribution and the sorts of messaging you're attempting in this thread. 

I've not found the way you're seeking to use mail to be particularly transportable across clients, nor particularly reliable.

What we now use as SMTP mail grew out of distributing ASCII text messages across disjoint and very unreliable networks — this is why SMTP is store and forward — and file attachments and MIME encoding and HTML have all been grafted onto it and onto clients, and with the occasional problems.

In that other thread, I'd look at the MIME encoding and have a look at the contents of the messages.

In this thread, I would not use SMTP mail for remote embedded images — this embedded links stuff is far too close to web bugs and also to security problems, when malware in some embedded scripting language is invoked for some of the file formats, plus there's that various folks can't or don't or won't load remote images as spammers use web bugs and there are malware attacks based on junk in messages, plus there's the generic HTML rendering mess that arises across different clients.

This before discussing how SMTP is not a particularly reliable transport for anything important.

That SMTP works as well as it does for this and for other purposes is still... surprising.

I wish you well in your quest.  On your way, you will be learning about HTML rendering and MIME encoding and SMTP messages and anti-spam and probably even some security here, too.   None of what I'm discussing here is specific to OS X, either.

To re-state an earlier comment: anybody that's interested with security or with avoiding spam will block those remote image loads.