Bookstack cannot send e-mails

I’ve installed the linuxserver.io docker container for Bookstack. In the .env file I configured the smtp settings in order to enable the sending of e-mails. But when I try to send a test e-mail from Bookstack I am getting this error:
Error thrown when sending a test email: The BCMath functions must be enabled to use the NTLM authenticator.

I tried to install the php bcmath extension with a file in the “custom-cont-init.d” with the content:
apt update -y
apt install php-bcmath

But this did not change anything.
Are there any other Bookstack users with the same problem? How did you solve it?

Hi there,

i have the same problem.
Is there any process or any workaround about that?

thanks

For me it helped to change the port in the .env. Is your bookstack instance and the mail server in a local network? try port 25