When attempting to update to 2.9.21 I get the following error:
The certificate for this server is invalid.
You might be connecting to a server that
is pretending to be “c-command.com”
which could put your confidential information at risk.
Would you like to connect to the server anyway?
In addition, the only option is “Okay” and the only way to close the dialog is to quit SpamSieve.