==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release): 1.6.5
- Deployed with iRedMail Easy or the downloadable installer? Download
- Linux/BSD distribution name and version: Debian 12.1
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Web server (Apache or Nginx): Nginx
- Manage mail accounts with iRedAdmin-Pro? No
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====

Hello,
I upgrade debian 11 to 12 server which tries to send email by IOS client, the postfix log is:

postfix/submission/smtpd[1492]: improper command pipelining after CONNECT from unknown[IP]: \026\003\001\002\000\001\000\001\374\003\003\305`5}e\375\377&iJT\001>\005\213\t\276\250\360Klv\377\r\177\023\333\335\230\213ym \321\312\345\346\224\022\355j\203\f[/2r\307$$\035\265,\315\3720F\302\234\342\345n6^\252\000***\023\001\023\002\023\003\300,\300+\314\251\3000\300/\314\250\300\n
postfix/submission/smtpd[1492]: warning: non-SMTP command from unknown[IP]: \026\003\001\002\000\001\000\001\374\003\003\305`5}e\375\377&iJT\001>\005\213\t\276\250\360Klv\377\r

As you can see it is a "non-SMTP command" given by Postfix. It works fine on MacOS.
I'm curious. What might this be?

Thanks for help.