Problems with sending email attachments to Windows computers.

I always send in plain text. If you don't the message is sent in two parts, one plain and one HTML. Also anything other than text in the HTML will be sent as an attachment.

the problem seems to be with Windows OS not recognising the attachment as a separate file. There is no problem sending files from Mac to Mac, or from PC to Mac

So what does that tell you about Windows? 😎

The fault is with the recipient.

As I said before, the problem seems to be with Windows OS not recognising the attachment as a separate file.

This is not a Windows issue but a mail client and/or user issue. For example in Thunderbird there is an option at View/'Display Attachments Inline'. John, nevertheless, needs a solution which works easily for most people he sends files to.

Unless I have misunderstood his easiest option is to always send mails as text and not HTML.

I have been having doubts about my earlier post. Perhaps I should do some tests and see if originating mail clients behave differently. I will attempt to compare Mail and Thunderbird with 2 attached jpg images.

Sorry about this John - it appears I was wrong. My tests indicate that Apple Mail puts the following 'header' before every 'attached' image. Content-Disposition: inline

Thunderbird uses. Content-Disposition: attachment

Both comply with http://www.ietf.org/rfc/rfc2183.txt but perhaps Mail should not claim these are attachments.

At the receiving end Thunderbird can override either one as the user wishes but it would be understandable if some mail clients do not have this flexibility.

Whilst I can add a permanent user 'Content-Disposition: attachment' header to Mail with a Terminal command it fails to stop Mail using 'Content-Disposition: inline' before each image.

Unless a fix for Mail can be found my advice is not to use it for your critical emails.

Here are some technical details:

Terminal command to view user headers if they exist:

defaults read com.apple.mail UserHeaders

Terminal command to add a user header:

defaults write com.apple.mail UserHeaders '{"Content-Disposition" = "attachment"; }'

Terminal command to remove all user headers:

defaults delete com.apple.mail UserHeaders

These headers are stored in:

~/Library/Preferences/com.apple.mail.plist

My three slightly modified test emails are below. I have replaced much of the six images with 'etc etc'. The three tests are:

1. Sent by Thunderbird
2. Sent by Mail
3. Sent by Mail with Content-Disposition: attachment' user header

MIME-Version: 1.0

Content-Type: multipart/mixed;

boundary="------------020708050309070703090401"

This is a multi-part message in MIME format.

--------------020708050309070703090401

Content-Type: text/plain; charset=UTF-8; format=flowed

Content-Transfer-Encoding: 7bit

Here are 2 flowers

--------------020708050309070703090401

Content-Type: image/jpeg;

name="images-1.jpeg"

Content-Transfer-Encoding: base64

Content-Disposition: attachment;

filename="images-1.jpeg"

/9j/4AAQSkZJRgABAQAAAQABAAD/ etc etc /9k=

--------------020708050309070703090401

Content-Type: image/jpeg;

name="images.jpeg"

Content-Transfer-Encoding: base64

Content-Disposition: attachment;

filename="images.jpeg"

/9j/4AAQSkZJRgABAQAAAQABAAD/ etc etc //2Q==

--------------020708050309070703090401--

Mime-Version: 1.0 (Apple Message framework v936)

X-Mailer: Apple Mail (2.936)

--Apple-Mail-5-200699550

Content-Type: text/plain;

charset=US-ASCII;

format=flowed

Content-Transfer-Encoding: 7bit

Here are 2 flowers

--Apple-Mail-5-200699550

Content-Disposition: inline;

filename=images-1.jpeg

Content-Type: image/jpeg;

x-unix-mode=0644;

name="images-1.jpeg"

Content-Transfer-Encoding: base64

/9j/4AAQSkZJRgABAQAAAQABAAD/ etc etc /9k=

--Apple-Mail-5-200699550

Content-Disposition: inline;

filename=images.jpeg

Content-Type: image/jpeg;

x-unix-mode=0644;

name="images.jpeg"

Content-Transfer-Encoding: base64

/9j/4AAQSkZJRgABAQAAAQABAAD/ etc etc //2Q==

--Apple-Mail-5-200699550--

Content-Type: multipart/mixed; boundary=Apple-Mail-7-204238499

Content-Disposition: attachment

Mime-Version: 1.0 (Apple Message framework v936)

X-Mailer: Apple Mail (2.936)

--Apple-Mail-7-204238499

Content-Type: text/plain;

charset=US-ASCII;

format=flowed

Content-Transfer-Encoding: 7bit

flowers

--Apple-Mail-7-204238499

Content-Disposition: inline;

filename=images-1.jpeg

Content-Type: image/jpeg;

x-unix-mode=0644;

name="images-1.jpeg"

Content-Transfer-Encoding: base64

/9j/4AAQSkZJRgABAQAAAQABAAD/ etc etc /9k=

--Apple-Mail-7-204238499

Content-Disposition: inline;

filename=images.jpeg

Content-Type: image/jpeg;

x-unix-mode=0644;

name="images.jpeg"

Content-Transfer-Encoding: base64

/9j/4AAQSkZJRgABAQAAAQABAAD/ etc etc //2Q==

--Apple-Mail-7-204238499--

Great work again, thanks for the extreme effort! 🙂

Great research, Neville! I should really visit here more often!

So from now I will be advising the forum members at InterMactivity.be (a Flemish Apple forum) not to use the Apple "Mail" app for critical attachments until a bug is fixed, am I right?

Some may disagree with your conclusion and Apple may not view it as a bug.

Much may depend upon the competence of users both ends.

An alternative which should work for many users is to zip critical attachments.

Many thanks indeed for your detective work as to what is causing this problem.

It seems that Apple expects that all other mail clients out there will automatically comply with what is probably in the standards somewhere and gives no option to make things easier for people on other systems with perhaps older software.

At least Thunderbird seems to work, in that Thunderbird on my Mac machine can attach a picture that will be correctly opened by Outlook Express but it is no more able than Outlook Express to open a picture attached to an Apple Mail message.

Enclosing images in a folder and attaching that, compressing the picture, and ending the message with an empty folder all work. Probably the last method is the least bothersome to use, though I have yet to test "Attachment Tamer" and "Zip Files for PC" for ease of use.

Also, in my case, rich or plain text seems irrelevant.

Lastly I join my voice to those who are screaming for a solution from Apple - this business is driving my wife nuts, as she is constantly exchanging pictures with PC users, and all she wants is easy-to-use efficacity which we all thought Apple stood for.

Have you tried Screenshots for shared pictures ( command 3 or command 4-and-resize/ add "shift" after "command" for azerty keyboards)? This will turn your desktop/picture into a .png. And smaller than the original, too.

Probably natively supported on Win XP and Vista.

Good luck!

Thanks, but as the pictures are already files in the machine, and a screen shot just produces another picture, I don't think this would help. Also, it is quite esy to transform a jpg into a png, as far as I remember with Preview.

No the problem here is one of how Mail treats attached images.

I have just tried and tested "Attachment Tamer" and installed it on my wife's machine as well - it is marvellous, it solves the problems, has extra facilities as well such as deciding how the icons' names will be displayed etc.,, the size of picture attachments is still selectable, and best of all it works completely transparently without one having to think of compressing files, adding empty folders etc. - it just works, which is what Apple used to be about.

PS a "single user licence" for Attachment Tamer covers 3 machines, thank Goodness, and they are also open to discounts for students and poor non-profit organisations etc.

Wow! Good suggestion to tell your corporate clients they suddenly don't know how to use computers any more.

Right click on the image and select View as icon