Assuming I have all the necessary hardware... I want to develop a system where you type in an email address and the Arduino will send hourly updates on attached sensors to the provided email address.

I can only get this to work if I enter my email account's username and password and send the email from the authenticated account. There's tons of examples online of this. However, I want to share it with others and I do not want my email authentication to be accessible or be attached with sending the emails. For example, I want the email to be from a generic service like email@web-mail.com that no one can sign into and not my personal email or a Gmail account I made for the project.

Anonymous email senders have the right method, but they require human interaction to bypass Captcha or similar.

Does anyone have an idea of how to do this? Or should I make a separate webserver that handles the requests made by the Arduino and send emails through a Gmail account I made for the project?

  • Even if you can get a basic SMTP connection going as per the answers already given, unless you use a registered domain with the correct SPF and/or DKIM settings etc, you may well find a lot of your emails rejected, and your "from" address blacklisted as a spammer.
    – Cylindric
    Jan 7, 2016 at 17:01

2 Answers 2


You may be able to do this by running the SMTP transaction yourself. You don't actually need a valid from address (though I probably shouldn't be saying that). There are a number of resouces for how to do this, here's a quick list:

If you read an article telling you how to do SMTP in a generic sense (not using a particular provider's infrastructure) and it looks like they want a "real" e-mail address, you can try with a fake one. Chances are decent that it may work.

There are some fine points that may cause you grief if you go for the most simple of implementation (for example, just because my e-mail address is foo@bar.org doesn't mean that bar.org will accept an SMTP connection, the "right" way to do it is to check DNS for an MX record for bar.org).

It would be best to do (and log) any errors that you encounter. There are plenty of things that can go wrong, so tracking where it blows up will help you – or anybody who's trying to help you debug.

If you don't want to roll your own SMTPClient and FullIP look worth checking out.


I am thinking that you will have a few issues in doing this,

If you wish to, as mentioned by dlu, run the SMTP Transaction from the device yourself, you are free to do that, however, most SMTP Relays will require some sort of authentication; this is to prevent me from using a random relay to send out millions of messages.

Another issue may be that if you do setup a local relay, your ISP will block traffic on port 25, which is common; this means your mail can never be delivered to an external server.

My thoughts on the simplest way to do this would be getting a Virtual Private Server that will run the mail service and a webserver; you could then make a simple PHP script that will accept a few parameters, and send an email.

Following the above, you would only need to make an HTTP request to your server for the mail to be sent,


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