Other Wordpress Plugins with Email Functions

first off great product.
I have a few Wordpress plugins that automatically send emails to my registered users. I noticed that after I installed the dhtmlxScheduler plugin the other plugins stopped sending emails. After deactivating the dhtmlxScheduler plugin the email function for the other plugins started working again. Any ideas.

Hello,

What’s your plugin name? Can I find it on the Internet to try to use it locally?

Best regards,
Ilya