Error list of the "Advanced Text Mail Initialisation" FBox

The "Advanced Text Mail Initialisation" FBox indicates an error, what can be the reason?

Error	meaning	possible reason
-3	Error establishing connection	Server address invalid
-25	Server rejects SMTP "MAIL FORM" command	Sender e-mail address is not a valid / existing e-mail address
-29	Server rejects "AUTH" command	Password or user of the mail server are not correct
-108	File open command	The file path of the attachment is not correct. If the attachment is on M2 Flash it has to be: M2_FLASH:/Webpages/filename.csv

Note that e-mail server can react in different ways. Some servers will accept non valid e-mail addresses as sender.