I can't send mail

I set two mail accounts in the eM Client - one POP3/SMTP and the other IMAP/SMTP. I can send mails from one account (IMAP/SMTP) but not from POP3/SMTP account. When I try to send a mail from this account, a pop up comes out (Title - Password required) saying “5.7.0 authentication failed”. Both account settings are same as I set in Outlook and Opera from which I can send mails using the same two accounts. Kaz

majority of similar issues is caused by pop3 account misconfiguration (wrong host, port, security policy or user name). So I would start by double-checking the settings anyway.