Curl SMTP on Linux Invalid From address

I got Thunderbird setup and can use that or the web client for the regular tasks, but need an automated way to send just a few emails. I’m trying to use ‘curl’ (8.7.1) which has worked well for this sort of thing with other email providers. It says I have an invalid From address, but I am using my default identity (not an alias). I’m getting the following error:

 curl -v --url 'smtps://' --ssl-reqd \                                         
 --mail-from ''  \
 --mail-rcpt <mytarget> \
 --upload-file body.txt \
 --user boxturtlebakery
* upload completely sent off: 112 bytes
< 550 Invalid From address. Please see

I can use something else to if someone has another open-source piece of software that works well with the Runbox services.

Thanks for any help.

Hello and apologies for the belated response.

We have tested the same commands with a test account and this appeared to work. We have replied to your support request regarding this matter and will follow up this issue there.

– Geir