web server freezes by the smtp server

I’m working on the project containing the basic web server and smtp server. I want to send an e-mail when running web server,
if smtp server ip address is set incorrectly, web server freezes about 60 seconds. if smtp server ip is correct, everythings ok. SNMP agent continues to work in this case. Smtp server running separate thread. I changed the smtp server and web server thread priority but problem continues. What is the problem Does anyone have any idea.

NET+OS 7.4.2
Device: Digi Connect ME -C JTAG