The communications are probably protected by the attorney-client privilege, and there is a special ethical rule governing interactions between lawyers and prospective clients. I'll quote Colorado's version of this widely enacted model rule at length along with its official comments:
Rule 1.18. Duties to Prospective Client
(a) A person who consults with a lawyer about the possibility of
forming a client-lawyer relationship with respect to a matter is a
prospective client.
(b) Even when no client-lawyer relationship ensues, a lawyer who
has learned information from a prospective client shall not use or
reveal that information, except as Rule 1.9 [conflicts of interest
with former clients] would permit with respect to information of a
former client.
(c) A lawyer subject to paragraph (b) shall not represent a client
with interests materially adverse to those of a prospective client in
the same or a substantially related matter if the lawyer received
information from the prospective client that could be significantly
harmful to the prospective client, except as provided in paragraph
(d). If a lawyer is disqualified from representation under this
paragraph, no lawyer in a firm with which that lawyer is associated
may knowingly undertake or continue representation in such a matter,
except as provided in paragraph (d).
(d) When the lawyer has received disqualifying information as
defined in paragraph (c), representation is permissible if:
(1) both the affected client and the prospective client have given
informed consent, confirmed in writing; or
(2) the lawyer who received the information took reasonable
measures to avoid exposure to more disqualifying information than was
reasonably necessary to determine whether to represent the prospective
client; and
(i) the disqualified lawyer is timely screened from any
participation in the matter and is apportioned no part of the fee
therefrom; and
(ii) written notice is promptly given to the prospective client.
COMMENT
[1] Prospective clients, like clients, may disclose information to
a lawyer, place documents or other property in the lawyer's custody,
or rely on the lawyer's advice. A lawyer's consultations with a
prospective client usually are limited in time and depth and leave
both the prospective client and the lawyer free (and sometimes
required) to proceed no further. Hence, prospective clients should
receive some but not all of the protection afforded clients.
[2] A person becomes a prospective client by consulting with a
lawyer about the possibility of forming a client-lawyer relationship
with respect to a matter. Whether communications, including written,
oral, or electronic communications, constitute a consultation depends
on the circumstances. For example, a consultation is likely to have
occurred if a lawyer, either in person or through the lawyer's
advertising in any medium, specifically requests or invites the
submission of information about a potential representation without
clear and reasonably understandable warnings and cautionary statements
that limit the lawyer's obligations, and a person provides information
in response. See also Comment [4]. In contrast, a consultation does
not occur if a person provides information to a lawyer in response to
advertising that merely describes the lawyer's education, experience,
areas of practice, and contact information, or provides legal
information of general interest. Such a person communicates
information unilaterally to a lawyer, without any reasonable
expectation that the lawyer is willing to discuss the possibility of
forming a client-lawyer relationship, and is thus not a "prospective
client." Moreover, a person who communicates with a lawyer for the
purpose of disqualifying the lawyer is not a "prospective client."
[3] It is often necessary for a prospective client to reveal
information to the lawyer during an initial consultation prior to the
decision about formation of a client-lawyer relationship. The lawyer
often must learn such information to determine whether there is a
conflict of interest with an existing client and whether the matter is
one that the lawyer is willing to undertake. Paragraph (b) prohibits
the lawyer from using or revealing that information, except as
permitted by Rule 1.9, even if the client or lawyer decides not to
proceed with the representation. The duty exists regardless of how
brief the initial conference may be.
[4] In order to avoid acquiring disqualifying information from a
prospective client, a lawyer considering whether or not to undertake a
new matter should limit the initial consultation to only such
information as reasonably appears necessary for that purpose. Where
the information indicates that a conflict of interest or other reason
for non- representation exists, the lawyer should so inform the
prospective client or decline the representation. If the prospective
client wishes to retain the lawyer, and if consent is possible under
Rule 1.7, then consent from all affected present or former clients
must be obtained before accepting the representation.
[5] A lawyer may condition a consultation with a prospective client
on the person's informed consent that no information disclosed during
the consultation will prohibit the lawyer from representing a
different client in the matter. See Rule 1.0(e) for the definition of
informed consent. If the agreement expressly so provides, the
prospective client may also consent to the lawyer's subsequent use of
information received from the prospective client.
[6] Even in the
absence of an agreement, under paragraph (c), the lawyer is not
prohibited from representing a client with interests adverse to those
of the prospective client in the same or a substantially related
matter unless the lawyer has received from the prospective client
information that could be significantly harmful if used in the matter.
[7] Under paragraph (c), the prohibition in this Rule is imputed to
other lawyers as provided in Rule 1.10, but, under paragraph (d)(1),
imputation may be avoided if the lawyer obtains the informed consent,
confirmed in writing, of both the prospective and affected clients. In
the alternative, imputation may be avoided if the conditions of
paragraph (d)(2) are met and all disqualified lawyers are timely
screened and written notice is promptly given to the prospective
client. See Rule 1.0(k) (requirements for screening procedures).
Paragraph (d)(2)(i) does not prohibit the screened lawyer from
receiving a salary or partnership share established by prior
independent agreement, but that lawyer may not receive compensation
directly related to the matter in which the lawyer is disqualified.
[8] Notice, including a general description of the subject matter
about which the lawyer was consulted, and of the screening procedures
employed, generally should be given as soon as practicable after the
need for screening becomes apparent.
[9] For a lawyer's duties when a prospective client entrusts
valuables or papers to the lawyer's care, see Rules 1.15A and 1.15D.