load a Rebex.totalpack.dll is taking one minute first time. second time it works fine

Suppose we have two method A and B and A is Calling B. B has Rebex SMTP class and its method. Once we setup SMTP server first time then A calls B. First time its taking 1 minute to enter into B method and execute first line of B method. Any specific reason? Rebex.Total.dll size is 2.01 MB.

Please guide further to resolve this issue.