Internal Server Error when trying to mass mail in Docker

SMTP settings are valid because test email works, what else can I do?

Exception while invoking method 'Mailer.sendMail' TypeError: Cannot read property '0' of undefined at packages/rocketchat:mailmessages/server/functions/sendMail.js:46:37 at SynchronousCursor.forEach (packages/mongo/mongo_driver.js:1107:16) at Cursor.(anonymous function) [as forEach] (packages/mongo/mongo_driver.js:887:44) at Object.sendMail (packages/rocketchat:mailmessages/server/functions/sendMail.js:45:38) at MethodInvocation.Mailer.sendMail (packages/rocketchat:mailmessages/server/methods/sendMail.js:18:17) at MethodInvocation.methodMap.(anonymous function) (packages/rocketchat_monitoring.js:2731:30) at MethodInvocation.methodsMap.(anonymous function) (packages/rocketchat:lib/server/lib/debug.js:71:34) at maybeAuditArgumentChecks (packages/ddp-server/livedata_server.js:1767:12) at DDP._CurrentMethodInvocation.withValue (packages/ddp-server/livedata_server.js:719:19) at Meteor.EnvironmentVariable.EVp.withValue (packages/meteor.js:1304:12) at DDPServer._CurrentWriteFence.withValue (packages/ddp-server/livedata_server.js:717:46) at Meteor.EnvironmentVariable.EVp.withValue (packages/meteor.js:1304:12) at Promise (packages/ddp-server/livedata_server.js:715:46) at new Promise (<anonymous>) at Session.method (packages/ddp-server/livedata_server.js:689:23) at packages/ddp-server/livedata_server.js:559:43