Username is missing in the mail Notification

Hello everyone,

i am somehow new to graylog and would like to please you for some tips and help. I have already installed graylog (version 6.1 over docker-compose on Ubuntu ) and every thing works fine . I have also configured the mail notification for that and it works also partly well but the problem is that i dont get the user name in the mail notification ( however in graylog GUI i see the user name ). I did some changes to the mail template like below but it did not work as i wanted:

${if backlog}
— [Backlog] ------------------------------------
Last messages accounting for this alert:
${foreach backlog message}
${message}
${message.fields.user}
${end}
${end}
and in the HTML template i did the following:

user name : ${foreach backlog message} ${message.field.user}${end} ... but i dont see the user name in the mail notification.

I would appreciate any kind of help, thanks !