I created a distribution group containing over 600 external contacts. I use the distribution group name to send my email on a weekly basis. I've been getting email from a lot of contacts with yahoo email accounts that they have not been receiving my email. I've checked their email account in the external contact and they are correct. I do not get undelivered messages because of using distribution group to send out my email. I have them put my email address in their yahoo contact book but still they can not receive the emails.
Please advise.,