Thunderbird does not ask for password when sending second mail !!!

[Jkhatri]

Dear all

I'm using thunderbird 13.0.1 on my ubuntu 12.04,

when I start Thunderbird for the first time during a day it asks for 
password to receive the mail , and it also asks for password when I send 
first new email or reply to any received mail, thats ok , but after that 
done successfully whenever I try send/reply to 2nd mail it does not ask 
for password it simply sends the mail. I want to configure Thunderbird 
to ask for password each and every time I send mail , is there any 
configuration available in Thunderbird ???


Thanks in advance

Warm Regards
./
Jatin khatri