Kontact configuration

Hey,
I am changing computers and I am migrating all applications from one computer 
to another, both computers have the same Linux Kde Debian SID system. The 
configuration of Kontact (Kmail) creates a problem for me that I cannot 
resolve. I have three POP3 mailboxes for two of the mailboxes I have not hadI 
am changing computers and I am migrating all applications from one computer 
toI am changing computers and I am migrating all applications from one 
computer to another, both computers have the same Linux Kde Debian SID system. 
The configuration of Kontact (Kmail) creates a problem for me that I cannot 
resolve. I have three POP3 mailboxes for two of the mailboxes I have not had 
any problem a little surprised anyway by the fact that we cannot enter the 
password of the mailbox at this time and that it is only requested at the first 
attempt to receive messages from this mailbox. For a mailbox managed by Yahoo 
I cannot access each time after a certain time I have the message indicating 
that the password is incorrect, I made several attempts by scrupulously 
checking the password without success, I access without problem by firefox to 
this yahoo mailbox with this password. On my old computer with Contact, I have 
no problem accessing this Yahoo mailbox.
I don't know what to do anymore. Could you help me solve this problem? 
another, both computers have the same Linux Kde Debian SID system. The 
configuration of Kontact (Kmail) creates a problem for me that I cannot 
resolve. I have three POP3 mailboxes for two of the mailboxes I have not had 
any problem a little surprised anyway by the fact that we cannot enter the 
password of the mailbox at this time and that it is only requested at the first 
attempt to receive messages from this mailbox. For a mailbox managed by Yahoo 
I cannot access each time after a certain time I have the message indicating 
that the password is incorrect, I made several attempts by scrupulously 
checking the password without success, I access without problem by firefox to 
this yahoo mailbox with this password. On my old computer with Contact, I have 
no problem accessing this Yahoo mailbox.
I don't know what to do anymore. Could you help me solve this problem? any 
problem a little surprised anyway by the fact that we cannot enter the 
password of the mailbox at this time and that it is only requested at the first 
attempt to receive messages from this mailbox. For a mailbox managed by Yahoo 
I cannot access each time after a certain time I have the message indicating 
that the password is incorrect, I made several attempts by scrupulously 
checking the password without success, I access without problem by firefox to 
this yahoo mailbox with this password. On my old computer with Contact, I have 
no problem accessing this Yahoo mailbox.
I don't know what to do anymore. Could you help me solve this problem?
Philippe MERLIN