Real number of recipients

Question

Hello,

What is the best (fastest) way to estimate or calculate precisely the number of recipients of an email containing nested Exchanges mailing lists?

I have tried parsing each addressEntry of each recipient recursively, but this method is very slow. 30s for 600 recipients, which blocks my plugin.

I tried with the GetExchangeDistributionListMemebers method. It's a bit faster, but not so much.

When composing an email and adding large mailing lists, Outlook estimates the number of recipients as I want, but I don't find this property in the object model or in the proptags.

Do you have a solution?

Thank you