Multiple Newsletter Emails

MailPoet is set up so that it automatically emails newsletter subscribers ‘once a day’ and ‘when there’s new content’on the blog. This has been working perfectly for the last couple of posts but this morning it went out 4 times, one every hour which was somewhat embarrassing. Any ideas what is wrong and how to fix it?

I read this post https://support.mailpoet.com/knowledgebase/duplicated-newsletters/ but I’m not sure it applies to me as my entire site got 174 page views yesterday and I wouldn’t have thought this would constitute ‘high levels of traffic’, would it?. I did edit the post a couple of times but surely this wouldn’t effect the newsletter as it isn’t new content? The delivery method is set to PHP Mail and the send settings are 70 emails every hour (only 17 subscribers).

Any help would be appreciated. Thanks in advance

Jack

https://wordpress.org/plugins/wysija-newsletters/