Certificate failure signed certificate in certificate chain when i try setup inbount email with imap

When i setup a new email accont for imap in inbound email, appears this error:

Certificate failure for [server url]: self signed certificate in certificate chain: /C=SE/O=AddTrust AB/OU=AddTrust External TTP Network/CN=AddTrust External CA Root
Por favor, compruebe su configuración e inténtelo de nuevo.

Port 143 is open. Not use SSL.

SuiteCRM Versión 7.11.6
Sugar Versión 6.5.25 (Compilación 344)

Can you help me?