Form will allow a space in the field

What are in your mail fields?

As below:

[ Moderator Note: Please post code or markup snippets between backticks or use the code button. ]

<p>Your Name (required)
    [text* your-name] </p>

<p>Your Email (required)
    [email* your-email] </p>

<p>Your Phone Number (required)
    [text* phone] </p>

<p>Your Message
    [textarea your-message] </p>

<p>[submit "Send"]</p>

Seems fine to me, i must have setup Contact 7 form loads of times and never come across this issue before.

So what are in the To, From, Subject and Additional headers fields in the Mail section?

Body

From: [your-name]
Email: [your-email]
Phone: [phone]

Message Body:
[your-message]

Mail:

To: my email address
From: [your-name] <[your-email]>
Subject: Enquiry via Website

Nothing out of the ordinary, as I say, it works perfect so long as I dont leave a space between first and surname!

Try changing the From line to

From: "[your-name]" <[your-email]>

Thanks, but this makes no difference.

OK. Then check your server log. If you can’t find any clue, try deactivating all other plugins and switching to the default theme.

Done, switched off all plugins (all of which I have used many times with Contact7, without issue), no change. So i tried default theme, no change either. I am still unable to send if there is a space in the name.