XF 2.2 Custom contact us field not working in email (placeholder help)

[SleepyStew]

So I am trying to add a selection box to the contact us which will be sent out in an email but I'm having some trouble.

I have set up a basic selection box in the contact us form which is the following:

Although I can't seem to pass the value of it into the contact us email.

The code for the contact us form custom section is the following:

<xf:selectrow name="topic"
     label="{{ phrase('topic') }}" required="required" hint="{{ phrase('required') }}">
     <xf:option value="None"></xf:option>
     <xf:option value="I lost my password">I lost my password</xf:option>
     <xf:option value="I need to delete my account">I need to delete my account</xf:option>
     <xf:option value="I would like to appeal a website punishment">I would like to appeal a website punishment</xf:option>
     <xf:option value="Other">Other</xf:option>
</xf:selectrow>

But I am unsure of how to access this in the email, I can see that they use placeholders like

$email

but this doesn't seem to be set (such as $topic) using the code above (which I assumed it wouldn't be)

Is it possible I have to initialise some placeholder?

I would appreciate some help figuring out how to have a custom placeholder usable in the contact email template from an inputted selection field.

Thanks!
SleepyStew