Mail works well... sometimes.

Currently around 400 messages sent, while 100 fail. The RetryTimes field keeps incrementing. Where can I look to see the actual details as to why it is retrying these emails? Nothing in the windows event log, yaf events or anywhere I else I know. I checked the SMTP server logs and it does not look like YAF is truly trying to send these emails.

The email addresses are valid, and other emails did send without issue.