"Off-net-IP detected" indicates you're trying to send on a non-Dodo network, and the reason you're blocked is because the Dodo outgoing server requires Connection security = none and no authentication on port 25. They say on that page that you need to set up authentication to send on non-Dodo networks, but they offer no instructions, even for mobile devices, e,g,, Android.

So, you can use webmail when you're away from Dodo, or apply a somewhat more complicated method of adding an account with secure connections, e.g. gmail, outlook.com, gmx etc., and adding your Dodo address as an authenticated sender when sending through one of those secure servers. A secure smtp server can be accessed on any network.

Thanks for response. The problem started when our nbn stopped working after a lightning storm. Instead of reviving it, because I was away studying, my husband bought a Mobile Wireless Broadband device from Telstra which got him back online but caused a problem sending emails, which sounds like the situation you have described. I however, because I didn't want to lose my dodo email address just yet, bought a dodo sim card and an unlocked device, and started up a dodo mobile wireless broadband account. Because it was a dodo sim card and account I thought the email sending problem would be over for me but not so. Dodo techs couldn't explain it and said I should ask the email client.

I'm not too conversant with wireless broadband, but it sounds like it's the same as conventional, wired internet access, except wireless, and separate from the cellular network. So, while you could send from your Dodo account via a Dodo SIM and the cellular network, you couldn't send over wifi on a non-Dodo network. In other words, turn off wifi on the phone to force sending on the cell network. That's awkward, so it's probably better to have a gmail or equivalent account that has your Dodo account registered as a sending address, and also collects incoming mail from the Dodo account. That should work on any wifi network and also any cellular network, if you have a working SIM.

I haven't been using a phone for Internet - it's a device that calls itself a 4G ZTE WiFi Modem. It was sold as an Optus prepaid but Optus told me that they didn't think it was locked and as I was having no trouble getting on the Internet I thought it was all systems go. But maybe it's causing the problem. I'll try your gmail solution - didn't know gmail would do that. If worst comes to worst could buy a generic-type device. Thank you very much for your help.