All my Mails send from CDO ( Classic asp) was stuck in Queue folder and no mails are delivering for a long while i sorted this issue right now and steps i followed are below
1. the very first issue was of Directory permissions then no mails are not even get in to the queue folder
Go to your Mail root folder , here it is C:\inetpub\mailroot for my server, there will be 3 folders for us to consider
1. Pickup
2.Queue
3.Badmail
the mechanism for mail is in an order from Pickup > Queue to Badmail
Mails that are unable to deliver in a defined interval will go to the badmail folder and these mails obeviously fail to reach the receipeint
first set permission to all these 3 folders
go to Windows Explorer
Map to this directory
Right click >properties> secrity > iusr_<ur computer name>
Advanced
Edit Windows Users for All Permissions
After this the queue folder will receive mails if it was failing earlier
After this if we are using SMTP Go and Create Firewall Exception Rules both inbound and Outbound FOR 25 ( ONLY IF YOU ARE SURE PORT 25 IS INVOLVED), and create rule for TCP and UDP and allow all incoming / outgoing connections
but when the case of ASP , CDOSYS ( later windows versions) might not be using port 25, in most cases Port 587 will be using
Go to Administrative tools > Advanced Firewall > Create inbound / out bound rules allowing port 587 for all in/out connections
DONE