Gmail checks the images for known harmful software. Sometimes, senders may know whether you've opened an email that has an image. Gmail scans every message for suspicious content. If Gmail thinks a sender or message is suspicious, images aren’t shown and you’ll be asked if you want to see the images.
Don't know if this is because I am using IMAP to connect to gmail so it doesn't really see them (but seems to work with other pictures emailed to me) or whether it is due to the iPhone 'embedding' the images rather than attaching them?
Photos sent as true attachments to the message are not embedded with the iPhone's Mail client. Photos sent as true attachments are displayed inline or viewed in place within the body of the message, which is not the same as being embedded.
Doing this with an email client on your computer, there should be nothing special or different with the photos emailed by your iPhone with your Gmail account. I regularly send photos with my MobileMe account from my iPhone, and I can save the photos sent with my MobileMe account from the account's server stored Sent mailbox with the Mail.app on my Mac. I haven't tried to save all photos sent from every sent message in my account's Sent mailbox in bulk, but the photos are sent as true attachments to the message.
If you receive many attachments to the emails you receive in your Gmail account, you might be smart to save them on Google Drive, where you can access them from any device with an internet connection and share them with others easily.
After saving a file to Google Drive from Gmail, you can very simply find and open it from inside Gmail.
How to Save Attachments to Google Drive From Gmail
To save files attached to an email to your Google Drive account right from the message in Gmail:
Open the email with the attachment.
Position the mouse cursor over the attachment you want to save to Google Drive. Two icons appear superimposed on the attachment: one for Download and one for Save to Drive.
Click the Save to Drive icon on the attachment to send it directly to Google Drive. If you have multiple folders already set up on Google Drive, you'll be prompted to choose the correct folder.
To save all the files that are attached to an email to Google Drive in one go, click the Save all to Drive icon positioned near the attachments. Note that you cannot move individual files to particular folders if you save them all at once, but you can move the saved documents individually in Google Drive.
How to Open a Saved Gmail Attachment in Drive
To open an attachment you just saved in Google Drive:
How To Download Images From Mailchimp
In the Gmail email containing the attachment icon, position the mouse cursor over the attachment you saved to Google Drive and want to open.
Click the Organize in Drive icon.
In the fly-open menu that appears, click the link to wherever you had saved the attachment. When you click it, Drive opens in a new window, with the attachment already selected.
If you have more than one folder set up on Google Drive, you may see Organize in Drive instead. You can opt to move the file to a different Google Drive folder before opening it.