Nothing! When you send an email with Yesware, we embed an invisible pixel at the end of your outgoing message. This way, when your message is opened, the tracking pixel loads and you’ll receive a notification letting you know. The best part? Your recipient won’t see a thing. Unlike read receipts, our tracking pixel is completely invisible. So, you gain insights while your recipient has the same experience as usual.
Similarly, Yesware doesn't change where your email is sent from (meaning we send it from your own email server) so there are no "sent on behalf of" messages that can trigger spam filters.
One thing to note, if your recipient has images turned off as one of their email settings when they receive a tracked email from you, they might see (depending on their email client) a message such as "Load images from this user?" This message is triggered because of the invisible pixel image that tracks email engagement. This is the same pixel-beacon approach that major email newsletter/marketing companies use to track emails. We find that most individuals usually have their email preferences set to display images by default, so they would not see this message.