I'm responding to your query as a non-GMX employee.
If I read you correctly, you are asking if GMX can be used to send and receive email with others. GMX.COM
is one of the best free web-based email programs. So far as I know it is not affiliated with Microsoft, Apple, Google, etc. You can use it online for webmail from any computer AND you can interface it with any email program installed in your own computer, PC or Mac.
I have used GMX for 5 years and am very happy with it. It is secure and easy to use. Incoming and outgoing mail is scanned for infections automatically. Attachments up to 50 MB are allowed and online file storage is "unlimited" (great if you have too many pics to fit on your camera chip on that long trip). There's an events and schedule calender and direct support. GMX can fetch from other email accounts (if they allow it) and most mobile phones interface fine. GMX is not big on trendy bells and whistles, but that keeps it easy to use and uncluttered.
That said, GMX doesn't work well with a dialup land-line connection, even up to the US phone line maximum of 50-54 kbps. Dialup isn't fast enough to prevent time-outs.
I use Firefox to access GMX most of the time and Internet Explorer 9+ works OK, too. I would expect all other browsers of recent vintage to work just fine.
Finally, GMX (at least last I tried in 2013) won't allow mass emailings to more than 25 addresses at a time. Usually this means you are OK with a short list but must resend the email for each group of addresses above 25. This is a good way of getting the spammers to go elsewhere.
Click here for the home page and get the account details:
Your free email account