Capture bounced emails back in appian cloud

If you have custom email sender defined in the from field that has a valid existing email address, bounce notifications are sent to this email address.
Give a try..
Check documentation: 
https://docs.appian.com/suite/help/25.2/Configuring_Custom_Email_Senders.html

Email can be a tricky beast. Out of my experience, a few questions:

- Do you send your email directly from Appian cloud?

- Did you set up SPF in your corporate email setup?

- Did you discuss this with your email admins?

Hi,

Appian Cloud doesn’t provide a built-in way to track bounced emails directly. Since the emails are sent through Appian’s own mail servers, we don’t have access to bounce-back details like you would with some third-party email tools.
One way to handle this is by using an external email service like SendGrid or Amazon SES. These services can give you bounce notifications through webhooks or APIs, and you could then bring that data back into Appian if needed.

If you're on Appian Cloud, I will suggest that you'd work with Appian Support to explore sending emails through an external provider.