"With a list of 1,300 names I get an error about 1/5th of the way through, which says "Error - Insufficient System Storage."
"Insufficient System Storage" (AKA. Too many recipients specified) is an error sent by your ISP SMTP server to warn you that you have reached the delivery limit for the current SMTP session, that is in this case the recipient number limit per session usually when sending in bulk mode. In fact, most ISPs have such limit and it used to be set somewhere between 100 and 200 or less. The best is to ask though.
You can avoid this problem either reactivating the Singly option or using the 'Group mails' setting. Just select 100 or 200 in order to force MaxBulk Mailer to perform a new SMTP connection every 100 or 200 recipients:
If the problem persists try to select a lower value. If you decide to reactivate the Singly setting you will very likely have to use a group and an interval anyway. This is explained here: How many people can I send an email to at once?
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