Verify if you have stored the eBlocker certificate in your operation system as well.
For some virus scanners you have to deactivate the virus scanner function “SSL Scanning” or “HTTPS Scanning”.
Here some examples:
Avast
Avira (Mail Protection)
Bitdefender
ESET
Older ESET products
GData (Email check)
Kaspersky
Neu: eBlockerOS 2.5 veröffentlicht Release Notes & Download