“Invalid mailbox syntax” with valid mailbox syntax

@beckhall sorry for replying so late I didn’t notice the email notification until now. Your additional header should be as following:
Reply-To: [your-email]

The shortcode (content of square brackets) should contain only field name, nothing else. You have available shortcodes in the header of the settings of your contact form (on tab Mail) just under the text In the following fields, you can use these mail-tags: just keep in mind this list of shortcodes is updated on form save so when you change your form you need to save it to see updated codes. Let me know if it worked for you.

@lorinc you say we need to
‘in your “Form” part you should have following tag: [email* your-email] and in Additional Headers you should have Reply-To:<[your-email]>’
I don’t know where in my form I need to put the [email* your-email] – where do I put this into my form (copied below)
Thanks

<p><label for=”name”>Name:</label>
<input type=”name” id=”name” name=”Name” /></p>
<p><label for=”Businessname”>Business Name:</label>
<input type=”Businessname” id=”Businesname” name=”BusinessName” /></p>
<p><label for=”email”>Email:</label>
<input type=”email” id=”email” name=”Email” /> </p>
<p><label for=”phone”>Phone:</label>
<input type=”tel” id=”phone” name=”phone” /></p>
<div class=”clear”></div>
<p>[textarea your-message class:TCGmsg placeholder “What can I help you with?”] </p>

<p class=”tcgContactBlocks”>[submit “GET IN TOUCH”]</p>

@espleyk But this is not how you supposed to create forms in CF7. You should use shorcodes. Check out some YouTube tutorials.

For example have look on this one:
https://youtu.be/4-Zcbo1Bxx0?t=330
or basically any other.

What worked for me (at least to get rid of the warnings) is the following.

In the ‘mail’ tab use

to: [email protected]
from: [your-name] <[email protected]>
additional headers: ‘Reply-To:[your-email]’