"Opened Email" constraint: Browser

[Anonymous]

When we use "browser" constraint for "Opened Email" filter, will it only renurn the cases when lead opened an email in a browser?

It's not quite clear to me as I think most people read their mail via email services like Outlook and the field 'browser' is not populated for them.

[Anonymous]

My understanding is that open email tracking happens when an image, usually a 1px transparent image . This requires that the email client allows downloading images.  Browser email clients usually load the images by default. Outlook on the other hand requires the user to allow images to load which affects your metrics.