chickadee » email-address » local-part->string-ci

Returns a lower case version of the local part of the address. Use this if you know that the MTAs for the relevant domain are not case-sensitive. You can also use this to deduplicate addresses with mixed case local parts for domains with MTAs that are not case-sensitive.

> (use email-address)
> (local-part->string-ci (email-address "Andy Bennett <ANDYJPB@EXAMPLE.NET>"))
"andyjpb"