Is there someone who can and will, in the next few days, install mailing
list software on a Linux site.

The host limits the number of message to be sent to 250/hr. There is a
weekly newsletter that now goes to 4000 addresses and the list is growing.
The software must support the following:

Form-based subscription/unsubscription (double-opt in/out preferrred)
Archive (preferably searchable)
HTML email (preferably send the content of a pre-formed webpage)
Admin tools that let you add subscribers without getting confirmation
(addresses from those who have already opted in)
Admin tools that let you Invite subscribers
Admin tools that let you schedule mailings in advance and not be online to
monitor the mailings when they occur
Offers subscribers a text-only option
Customize the public admin pages (like for subscribing/unsubscribing and the
archive) to resemble the GUI of the newsletter or another CSS-based website.

It might be any of the following, I¹m not sure which of them will support
the above:

Mailman
Mailing List
jclement
mlmmj
PHPMyList
Majordomo
Minimalist
ezmlm-idx

A small budget available for this job. Please contact me off-list about the
job.  Thank you.

KK