In Apple mail I get an error message when clicking on SEND LATER button. \”An unknown error occurred. Please try again later.\” I have updated MailButler and logged out and in and restarted. It was working just a few days ago. Version 2525 (13060) Mac Mail Version 10.3 (3273)
I also have the same problem. Just started this week. Mac 10.13.4, Mac Mail 11.3.
Thank you for contacting us. We are aware of this bug and our development is currently working on fixing this as quickly as possible!
Thank you in advance for your patience!