Direct messages I send via website are not getting received



Our software automates the sending of “reminder” direct messages to our clients’ students from client’s account. The example of such DM is: “@studentaccount vandaag heb je rijles van 10:00 tot 11:00”. All these messages are the same, except times and recepients are different.

The problem is that not all these messages are reaching their destination, the recepient’s DM inbox. We know that the intended is following our client and is not blocking him.

As all of these DMs are almost identical, sent to several accounts a day, every day, with only the times changed, could it be that spam filter is catching these messages. If so, how to prevent that from happening?