EasyBlog post emails very slow and did not finish goint out to users

We have website that created a post on Friday Jan 25 2019. The posts did not start going out to users until Sunday the 27th and only about 70% of them were sent as of Monday the 28th. The site has approx. 900 users.
The Cron job is good and has been working fine for years and I don't see any server interruptions over the weekend.
Any ideas on why this might be happening?
Thanks