TOO MANY FAILED AUTHENTICATIONS

I have both a telefonica router and a TP Link router D7.  I do not use them both at the same time I merely interchange if I have a problem.

I also have Microsoft Office 2011 for Mac upon which I fully use the Outlook email system in preference to  Apple's mail system.

Recently, I have begun to experience problems with my emails  in that I have received the message "Too many failed authentications".

I have changed nothing in my setup so I am at a loss as to what is the cause of the problem.

After receiving this message I am unable to send emails on the telefonica account so I switch to the icloud to send them.

I am still able to receive emails to both the telefonica and icloud email accounts.

On the telefonica email account I have not checked the boxes for Override default port, SSL to connect or Always use secure password

in either the incoming or outgoing server.

I am using IMAP.telefonica.net incoming and smtp.telefonica.net outgoing server.

For the smtp server I am using the authentication: use incoming server information, but I have also tried using the user name and password but neither clears the problem.

I have spoken to apple support but they cannot assist.

Microsoft do not answer any queries.

All in all I find that neither company seems interested in what I surmise to be a simple problem, which is frustrating to say the least and appalling in a customer service respect.

Is there anyone in the community that has the wizardry to assist me in my plight?

Regards