When attempting to send an email campaign via EXM using a custom SMTP, the process might encounter issues. This might result in the failure to send emails, leaving the campaign in a Draft state and generating the following exception:
Chilkat mailman unlock code has expired. Please obtain a new unlock code
This issue arises after upgrading the ChilkatDotNet48 library to version 9.5.0.93 or later, due to a known Chilkat issue. The upgrade affects the handling of TLS connections, potentially leading to these failures.
To resolve the issue, download and install the pre-release compatible with the affected product version: