This is usually not caused by LUCY. If we cannot establish a SMTP connection, we won’t retry until a few hours have gone by. This is easy to verify: LUCY tells you if all emails have been sent. Usually this is done within seconds or minutes and can be tracked with Wireshark or similar tools. If all the emails have been sent, then technically there is nothing left for LUCY to do to accelerate the delivery. So in over 95% of cases, the process of delivery takes less than a minute. In a few cases, the message could take as long as 5 days to complete its trip from sender to recipient. It rarely takes more than 5 days as one of the SMTP servers will send the message back as undeliverable. And yes, the email that contains the Error message could take 5 days to get back! You also have to remember that there is a lot of software and hardware in between that your email has to pass through to get from the point of origin to its destination. Whether it is server hardware, software, routers, switches, copper or fiber optic cables, power grids, or even your own computer, there are many potential points of failure along the way. If any one of these has an outage or is overloaded, a delay can occur.