How to export all contacts from mail?

Question

Email

I have an email in my domain zone.
The hoster suggested using SquirrelMail webmail. I have already accumulated a lot of correspondence there.
How can I export all the email addresses I've had correspondence with?
SquirrelMail does not have an address book, there is no way to export it.
I connected to this mail via Outlook. All letters were loaded, but the Contacts folder was not created.
Help, please, what to do? How to export all contacts?