eMails failing to be sent can have at least 2 reasons that I know of.
First you have to make sure you have an IP adress provided by your GSM IP connection. You will need this to connect to your SMTP server.
Then you have to connect to an SMTP server, and bypass built-in security procedures by your Internet Services Provider (for instance the number of emails you send per minute is often limited). I got this part working using SMTP2GO to bypass gmail securities.
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