Thanks to all (K Shaffer, jsd2, and dbsneddon) who have responded as of this writing. I appreciate your input.
I know that it is possible to send this group email with the To: field either blank or addressed to myself while populating the Bcc: field with the actual recipients. I'd prefer not to do that as I'm certain that, at one time, I was successfully able to send the email with a generic recipient name in the To: field. I
think that I may have put the generic name in parentheses, as in "(Newsletter Subscriber)", but if that was the case, that no longer works, either, as the To: field ends up blank on the receiving end when I now test that option.
Considering that the second warning box seems to be generated by my ISP, I'm thinking that my ISP may have made some change on their end that now prevents the sending of email if the To: field is not populated by an entry that looks like some sort of email address, real or fake. So, unless I receive any additional responses to this issue, I'll probably just enter my own email address in the To: field, as has been suggested. (My experience with leaving the To: field blank is that, more often than not, the field then appears blank to the recipient, and I would prefer to avoid that.)
Thanks,
Paul