Problem sending email in a live test

[ClemeK]

Hi, I am having a problem, I was wondering if someone can tell me what I am doing wrong, or where to look.
I'm using version 3.2.0, and coding in C#

I have written a small program that, that should send out a set of emails, in test mode everything appears to be fine. I then decided to do a “Live” test, I change all the emails to be sent too, to be ones I own (a Gmail account), and then did a send from another account (an Outlook account) and I then get an error message.

System.AggregateException: 'One or more errors occurred. (Syntax error, command unrecognized. The server response was: )'

This is being thrown on the send line:
var email = Email
.From(senderEmail, senderName)
.To(toAddress, toName)
.Subject(subject)
.Body(body)
.AttachFromFilename(file)
.Send();

All the fields appear to contain the correct information.

I tried swapping the email address so it went from Gmail to my Outlook\Hotmail address but I get the same problem.