Smtp and delete problem

[N P List]

Hey All,
Sorry about my multiple posts earlier.  I thought my Thunderbird wasn't 
sending out the mails.  Anyhow, can someone please help me with SMTP 
error, when sending mails:
SMTP Error in /srv/www/htdocs/webmail/program/steps/mail/sendmail.inc 
(185): SMTP error: Failed to add recipient

I can now login, check mails etc.  However, I can't delete mails.  I'm 
wondering if the delete problem is related to Postfix. 

Thanks,
Nitin