Every time you send email campaigns through our platform, a minuscule invisible image pixel is embedded at the bottom of your HTML email. This open tracker image pixel is unique to each campaign and each contact.
When a recipient opens your email with images enabled, that pixel is downloaded from the mailing server, and it registers as an open in your campaign report. Automated responses, like out-of-office messages, typically do not trigger the download of this graphic, so they shouldn't count as opens.
Open tracking via the image pixel is the standard method and provides a useful overview of your contacts' engagement. However, it does have limitations. It works only in HTML emails and not in Plain-Text campaigns, as images cannot be included in Plain-Text emails. Additionally, open tracking won't function if your contacts or their email client settings prevent image display.
In most of the email clients, the images are by default disabled hence system won't able to track it.
E.g. In the Outlook Email Client
Most of the web-based email inbox provides images visibility are by default enabled but it won't work in the spam or junk folder.
You can ask your contacts/subscribers to add you (sender email address) to their email address book or enable the image's display option in their email client to get more accurate open tracking.