Subscribe cannot sign in

Issue Summary
people cannot subscribe anymore → Français à Londres - Magazine
It should normaly send the confirmation e-mail but it doesn’t

the mailgun is well setup it does send the newsletters :
“mail”: {
“transport”: “SMTP”,
“options”: {
“service”: “Mailgun”,
“host”: “”,
“port”: 587,
“secure”: true,
“auth”: {
“user”: “xxx”,
“pass”: “xxx”

Setup information

Ghost-CLI version: 1.18.1
Ghost version: 4.36.1

Node.js Version
Checking system Node.js version - found v14.18.2

How did you install Ghost?