Does Outlook cache attachments when composing an email?

Question

This is something that I consistantly wonder about when I send an email that includes attachments.

Say I'm working on a Word document and I want to email it to some co-workers. I open up Outlook and click the Attach file button to attach my Word document to the email. However, before I click Send, I realize that I want to make a last-minute change to the document, so I quickly switch to Word and modify the document, and then click Save. Do I have to remove the attachment in the email and re-add it? Or will the newest version be sent?

Essentially, I'm asking if Outlook will cache a copy of the file to be sent with the email as you're composing it.

Answer 1

I don't really know, but I'm confident to say that, yes, it seems like does cache them.

When I compose a mail and attach a file. I can then delete that file from my hard drive and the mail is still sent fine. I will also receive the mail with the attachment intact.

This leads me to the conclusion that the file must be copied as soon as I attach it.

By running Process Monitor, we're even able to see where the file is copied and how:

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Answer 2

I was curious about this as well so I gave the following a shot:

1. Open new word doc.
2. Edit doc, save file.
3. Attach to an open outlook mail.
4. Make a second edit to word doc, click save.
5. Send email.

The attachment received contains the first edit, but not the second edit.

I also checked to see whether closing the word document before sending matters, it does not. The behavior is the same... so I'm reasonably certain the only way to get the current state is to attach the file AFTER it's been saved at whatever state you want it to be sent.