Dave-
That helped out a lot. Thanks for the link. It was an issue with one of the user's email address. It probably isn't validated on the exchange side.
I used this to build out my email string:
<sql:query var="et">
SELECT
SUBSTR(MAX(REPLACE(SYS_CONNECT_BY_PATH(email, '/')
,'/',';')),2) emailTo
FROM (
select MVL2.*,
row_number() OVER (Partition by ID order by ID) ROW#
from
(select
g.id,
u.email_address email
from
cmn_sec_groups g
JOIN cmn_sec_user_groups ug on g.id = ug.group_id
JOIN cmn_sec_users u on ug.user_id = u.id
JOIN cmn_captions_nls cc on g.captions_pk_id = cc.pk_id
where
cc.table_name = 'CMN_SEC_GROUPS'
and cc.language_code = 'en'
and g.group_code = 'process_managers')MVL2)
START WITH ROW#=1
CONNECT BY PRIOR ID=ID AND PRIOR row# = row# -1
GROUP BY ID
</sql:query>
<core:set value="${et.rows[0].emailTo}" var="emailTo"/>
The second I removed the user in question, it worked.
Thanks for the help!