SendMail[
 "From" -> "myemail@myisp.com",
 "To" -> "recipientemail@isp.com",
 "Subject" -> "Example Message",
 "Body" -> "Test",
 "Server" -> "smtpout.secureserver.net",
 "EncryptionProtocol" -> "SSL",
 "FullName" -> "MyUserName",
 "Password" -> "myPassword",
 "PortNumber" -> 25 (* I also tried 465, 587 *),
 "ReplyTo" -> None,
 "ServerAuthentication" -> Automatic,
 "UserName" -> "myUserName"
 ]

SendMail[
 "To" -> "YYY...@me.com",
 "Subject" -> "Example Message",
 "Body" -> "My text",
 "From" -> "xxx...@gmail.com",
 "Server" -> "smtp.gmail.com",
 "UserName" -> "xxx...@gmail.com",
 "Password" -> Automatic,
 "PortNumber" -> 587,
 "EncryptionProtocol" -> "StartTLS"
 ]

SendMail["To" -> "x@y.com",
 "Subject" -> "Example Message via Microsoft", "Body" -> "Keine Fehler!",
 "From" -> "xxx@myCompany.com", "Server" -> "outlook.office365.com",
  "UserName" -> "xxx@myCompany.com", "Password" -> Automatic,
 "PortNumber" -> 587, "EncryptionProtocol" -> "StartTLS"]