I have a Drupal 7 site with about 20,000 members. Sometimes I need to email them all at once. Thus far, I have been adding a rules component (Condition: Make sure user has not opted out of emails, Action: Send email, translated as appropriate for each language) and then used VBO and a view to select all the users on the site.
Unfortunately, with such a large number of users, even when VBO is queued to send emails 10 at a time the batch often encounters some error every few thousand users, so I need to find which user was last e-mailed when the batch error occurred and restart the batch manually.
Is there a more robust (i.e., automatic way that will not break and require manual intervention on my part) to email all the user accounts on the site when the number of users is large?