Gmail does not recognize an email address for no apparent reason

Question

When I attempt to address my email message by selecting a group and hit SEND I get the error message:

The address "seeminglygoodemail@example.com" in the "Bcc" field was not recognized. Please make sure that all addresses are properly formed.

If I select this particular email by itself it works. I've verified that the email is well formed.

Answer 1

It seems that the email address had a bad character that is not visible. Perhaps a Unicode 2-byte character that Gmail is displaying properly but storing as two bytes and tripping up its own parser.

The solution is to simply re-enter manually the email address.