@ mcolantoni
You don’t say exactly what version of avast you were using before the uninstall (no traps or tricks), latest version is 8.0.1497 ?
What is your email/ISP mail server and crucially does it use SSL/TLS (secure email) connections ?
What is your email program ?
What are the email errors being displayed ?

This information is crucial as earlier versions of avast, version 7.0.x used a different method for scanning, in avast version 7.0 the email account settings had to be changed by the user to allow avast to scan the content and then make the secure connection to send the email. These changes would have to be reversed in the email program by the user.

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What really would have helped you out would have been to seek help about the original problem (Trading) as there are many such instances in the forums where we have been able to help with this.

Typically it is about streaming data not using strict HTML protocol and this messes with the web shield that expects the HTML protocol to be used in html connections.

It is possible to add the IP address of the trading site to the Ignored addresses.