why does formail -xSubject: have a leading space?

Have I missed something?

SUBJECT=`formail -xSubject:`

leaves me with ' The subject'

why the space before the word 'The'?

I tried

SUBJECT=`formail -xSubject: `

and

SUBJECT=`formail -xSubject:\ `

and neither seemed to help....

Am I being obtuse?

TjL