Hello Walter,
Thanks for the inquiry. I do know we had corrected a scenario where some of the POP connections over SSL would fail. If you can please provide us a sample of the POP Retrieval logs for the time period we may be able to review further. Are your logs set to 'Detailed ' ? There may be more information in the logs. I'm not certain if the issue occurs for the same accounts each time.
Please consider opening a Support ticket so we can review this matter further. Are you licensed for SmarterMail 13.x ?
Thanks.