On many sites there are one of two contact forms used, one is called Form Manager (generally very old sites) and the other is called FS Contact Form. Neither of these form handlers are available now through the WordPress repository. Neither of them are supported any more by their authors. It is very much in your interests to replace them.
I am recommending the removal of the existing contact forms on all websites and replacement with Contact Form 7 and another plugin called Contact Form Redirection.
Both of these are supported contact forms and have current versions compatible with WordPress version 4.9.5.
By using these two plugins it will be possible to achieve the following:
- Contact Form similar in appearance to your current form
- Ability to upload an attachment
- Supports Google Recaptcha version 2.00 (to reduce spam).
- On screen message to sender to confirm message has been sent
- Redirection to a Thank You page
- Ability to format the message that is returned to your organisation
- Send a copy of the submitted message to the author to confirm submission
It can probably do many more things, but these are a superset of what we are currently supporting on the most advanced sites.
The downside is Contact Form 7 is not that intuitive to use if you are a novice user compared to the former versions. However it is one of the most popular plugins for managing user forms.