Duplicate Emails, sometimes MANY

I’m using SendGrid to process the emails, and my site gets a decent amount of traffic around the clock (at least 50 visitors per hours in the middle of the night, 100-300/hr during the day), and I’ve always had the MailPoet Cron turned on (though not using a custom cron on my server). So, my situation doesn’t seem to fit the circumstances described in your knowledge base article.

I’ve just checked my cPanel account to double check that I hadn’t added in a cron job and then forgotten, and there are no cron jobs set up at all.

My website is hosted on a VPS.

I’ve been using MailPoet to send my automatic newsletters/post updates for about a year now. About three weeks ago, I made a new post on my site, and in the morning, I got 4 copies of the email from MailPoet, and other users got 8 or 10 copies. It was the first time that I’d had the problem. I don’t have a huge email list… just about 1000 people, and I lost about a dozen of them from that mishap.

I didn’t know what was causing the problem and was traveling out of the country, so I optimized my database, rebooted my server, and hoped it wouldn’t happen again, and it didn’t until this morning (maybe 6 new posts in the meantime).

This morning, I got two copies of the email. One of my colleagues got 4, and looking at my logs, it appears that someone got 8 (and he unsubscribed).

I’m at a loss as to what could be causing this, and I’m concerned that some servers have just started blocking me as a result.

My website is http://www.lightandmatter.org, for what it’s worth.

I’m in the process of setting up a cron job anyway, since it’s the only thing I can think of to try, but I’m not optimistic.

Any suggestions? Thanks!