what is the motive of introducing a delay of replaying of 50 log files and 24 hours? does that also means that log files on the production box will get truncated by the backup as soon as they are copied to the SCR box or it will not truncate those 50 log files ? if the target box needs to an exchange 2007 mailbox role or i can specify hub transport as the target as well ?

Log files get truncated after all SCR targets have copied and inspected them (and a backup completes on the source), truncation on source doesn't wait for those to be replayed by SCR targets - these could be set to different replay delays on different targets. Reason to configure the delays: If the source is corrupted, the target does not get corrupted soon and there's time for recovery (by activating the target) if required. On the target, truncation happens when both of the following are true: - Log file sequence (number) is lower than the checkpoint. (The checkpoint points to the log below which all logs are committed/replayed to the Database) - AND log file is older than replay + truncation lat times. More: Standby Continuous Replication http://technet.microsoft.com/en-us/library/bb676502.aspx

good job!!!