Are you creating the mail with Mail::fake()? You could assert against know data by altering your mail fake assertions
Mail::fake();
Mail::assertSent(NewOffer::class, function ($mail) use ($user) {
return $mail->hasTo($user->email) &&
$mail->hasSubject('your-subject') &&
$mail->hasFrom('your-from');
});
I am not positive it will work but worth a try.