Use a CDN for images in e-mail

I have the same problem that the one described in Email images do not appear in Gmail/Web, but in my case it’s because the Passbolt platform is not registered publicly and I don’t want to expose it on the web. It should stay in a secured network, only accessible using a VPN for example.

Could I change some installation parameters to use a public CDN for displaying images in email , or is it a feature request ?

I’m familiar to this problem, we’ve not found a solution yet when the site is not reachable by Gmail because it is on an internal network. This would warrant a feature request I think.

I’m not sure how the CDN option would work. Could you elaborate on this?

One option would be to allow passbolt system administrators to switch to a mode that uses inline attachments with a Content-ID (CID), as this technique works with Gmail. Passbolt in this mode would be adding the images as inline attachments to the email and would need to point CID URLs instead of Data URLs in the html body of the email.

I thought about a CDN, or any other way to tell Passbolt to use a different endpoint for the images embedded in the e-mails. In my mind it could work like this :

A new optional environment variable called EMAIL_IMAGES_BASE, that would by default use the APP_BASE value. In my case, I will be able to host the images on another server, outside the secured network. Passbolt could also provide a public server where images of the latest version would be hosted.

I’dont know if it could cause any security issues.