We're going to use If This, Then That, or IFTTT, to create a system that automatically sends any new Gmail attachment to your Dropbox account, where it can be more easily organized and accessed. If you've never used IFTTT before, you may want to read our IFTTT primer first. Otherwise, let's get started.
Create a trigger
Login to IFTTT and click Create a Recipe from the dashboard. On the next page, the phrase "ifthisthenthat" appears with the word "this" highlighted. Click it, and you'll arrive at a veritable app store of trigger channels. Scroll down to the Gmail icon, or use the search field to jump to it, and select it.
The page will automatically scroll down to a grid of various Gmail Triggers--sets of conditions that will instigate a desired response. We're interested in email attachments here, so click on the "Any new attachment" box. Click Create Trigger. The phrase "ifthisthenthat" will appear again, only this time the word "that" is highlighted. Click it.
Define the action
You've created a trigger that will fire every time you receive an email with an attachment. Now it's time to define what you want done with it. Select Dropbox from the list of available action channels, and then click the "Add file from URL" box from the grid of possible actions.
You'll be presented with a list of "action fields"--File URL, File Name and Dropbox Folder Path--each of which has a drop-down menu of "ingredients" you can add and arrange to define that action.
Because we're separating attachments from their original emails, it's critical to name them so they're easily identifiable. Fortunately, IFTTT provides several options you can arrange into relevant naming schemes. To do this, click the beaker icon to the right of the File Name field and select as many ingredients as you want from the drop-down menu in the order you want them to appear in the file name. An ingredient list of {{AttachmentFilename}} {{FromAddress}} {{Subject}} makes a pretty effective naming convention, though you should, of course, use one that works for best you.
Similarly, click the beaker next to the Dropbox Folder Path field to define where your email attachments will be saved. The default path is "IFTTT/Gmail," but you can enter your own or have one created automatically based on ingredients such as the sender, the date of receipt, or the email subject line.
Once you've defined these fields, click Create Action. Now all incoming email attachments will be automatically added to your Dropbox account.