==== REQUIRED BASIC INFO OF YOUR IREDMAIL SERVER ====
- iRedMail version (check /etc/iredmail-release):
- Deployed with iRedMail Easy or the downloadable installer?
- Linux/BSD distribution name and version:
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):
- Web server (Apache or Nginx):
- Manage mail accounts with iRedAdmin-Pro?
- [IMPORTANT] Related original log or error message is required if you're experiencing an issue.
====
v1.4.2
Downloadable installer
Linux Debian 11
MariaDB
Nginx
No
Here is the error I get from two different email client whe to trying to send mail ... to anywhere:

An error occurred while sending mail. The mail server responded: 
5.7.1 <them@example.com>: Recipient address rejected: Sender is not same as SMTP authenticate username.
Please check the message recipient "them@example.com" and try again.

I read about this on the net but found just general tips.  I tried sending to a local user on the same domain, and then to an outside one, but neither work and give this error.  But then, oddly, I set up Mac Mail and everything works great!  It's like the Mozilla (Seamonkey) and ex-Mozilla (Thunderbird) curse!  Has anyone seen this weirdness?

Regards,
Steve