I don't think so. If Pegasus Mail is configured to suppress BCC then the resulting header in the message received by the BCC recipients can be "BCC: (Suppressed)". As has been stated, the SMTP service provider may not honor whatever Pegasus Mail tries to do. Yahoo apparently won't deliver when BCC is suppressed.

I am still curious to here what Yahoo does with a message sent To: a distribution list that is configured to suppress recipient addresses.

I just discovered that Outlook REALLY takes BCC suppression seriously. Suppressed BCC messages sent to my outlook.com account do not contain my outlook.com address anywhere in the headers. Ones sent to my gmail.com and zoho.com addresses contain it in a Delivered-To: header (other BCC addresses were suppressed). We must face the fact that we are at the mercy of the email handling servers, both on the sending end and on the receiving end. All that can be done is to try to figure what yours are doing and then find workarounds as best you can.

@BrianFluet, to answer your question: Yahoo reveals the email addresses in a Distribution List sent from Pegasus but the recipient can only see them if they are using a viewer like Pegasus's "Raw Data" view, and Yahoo does this when the Distribution List is entered in the "To:" box, and when it is entered in the Special > Blind CC box.

I agree with you that "we must have face the fact that we are at the mercy of the email handling servers". Yahoo could even decide to go a step further towards "transparency" by including an clear and unmissable indicator in emails that the email has been BCCed to others, and I might only discover this after the event. That would be embarrassing.

So perhaps one should avoid using BCCs, and simply endure a few more keystrokes to retrieve and then forward a copy of an email to a person who formerly one would simply BCC. Better to be safe than sorry.

In the configuration settings of the distribution list was the "To: field:" field populated? If so, was it in the form of a valid email address?

@BrianFluet, yes, Yahoo places the addresses in the Distribution List on the line beginning "X-Apparently-To:", and, yes, in the settings of the Distribution List which was used the "To:" field was populated with a valid email address.

After I wrote to a friend of the same vintage as myself about this matter this week, he responded saying:

**The whole point about Blind Copies is that recipients who have NOT been BCC'd have no idea:

1. WHETHER anyone HAS been BCC'd;
2. WHO has been BCC'd.**

I replied saying that I remembered his definition from the long-past days of memoranda circulated by civil servants in paper form only.

I considered BCC's would serve one of two purposes.

1. Conceal the identity of recipients.
2. Keep the email address of recipients private. I get pretty aggravated when I receive an email from a group, like a homeowners association, where that email contains the email address of every member. IMHO, distribution of my email address without my permission is wrong.