ThermoWorks RTR-500GSM WIRELESS LAN OR GSM (CELLULAR) LOGGERS - Manual (Page 13)

*Determining E-Mail Authentication Type
This procedure can be used with many E-Mail servers to determine what authentication will be accepted.
1) Open the Cmd prompt. Then type:
telnet <server_name>
<smtp_port_no> (return)
2) After server response, Type:
ehlo <your_domian_name> (return)
3) The server will respond something like the following:
In this case you can see that Earthlink
accepts PLAIN, LOGIN and CRAM-
MD5 smtp authentication. Since
LOGIN is accepted the RTR-500W
will work fine with this server.