The latest lucee version (188.8.131.52) seams to have a bug in cfmail, when serveral mail-addresses are set in [to] with delimiters:
Attribute [to] of the tag [mail] wasn’t a valid email address [actually bad email address]
Don’t forget to tell us about your stack!
OS: Windows Server 2016
Java Version: 1.8.0_161-b12
Tomcat Version: 8.5.5
Lucee Version: 184.108.40.206