In /etc/postfix/main.cf I only have:

myorigin = gmail.com

If I use:  
myorigin = syscon8@gmail.com

I get an error message;
Aug 31 14:28:02 i5 postfix/smtp[25841]: 1A31217E00EC: to=<root@syscon8@gmail.com>, relay=smtp.gmail.com[142.250.99.109]:587, delay=0.54, delays=0.01/0/0.5/0.03, dsn=5.1.3, status=bounced (host smtp.gmail.com[142.250.99.109] said: 553-5.1.3 The recipient address <root@syscon8@gmail.com> is not a valid RFC 553-5.1.3 5321 address.

my /etc/postfix/sender_canonical 
/^root@gmail\.com$/ syscon8@gmail.com

On Sat, Aug 31, 2024 at 2:17 PM Michael <confabulate@kintzios.com> wrote:
On Saturday, 31 August 2024 20:34:49 BST syscon edm wrote:
> Sorry, the cron entry should be:
> 55 12 * * * mv /var/spool/asterisk/monitor/* /home/thelma/mon/
> 1-5 is Monday to Friday
>
> mail.log:
>
> Aug 31 13:24:01 i5 postfix/qmgr[32301]: 0880F17E00EB: from=<
> syscon8@gmail.com>, size=699, nrcpt=1 (queue active)
> Aug 31 13:24:02 i5 postfix/smtp[9110]: 0880F17E00EB: to=<root@gmail.com>,
> orig_to=<root>,

You probably have in your /etc/postfix/main.cf:

myorigin = $some_user@some_domain.com

where some_user@some_domain.com is not syscon8@gmail.com, but root@*?


> relay=smtp.gmail.com[142.250.99.108]:587, delay=1.3,
> delays=0.02/0.01/0.55/0.68, dsn=2.0.0, status=sent (250 2.0.0 OK
>  1725132231 98e67ed59e1d1-2d85b0fdf44sm6088797a91.6 - gsmtp)
> Aug 31 13:24:02 i5 postfix/qmgr[32301]: 0880F17E00EB: removed
>
> Gmail is accepting the mail but it is sending to "root" instead of "syscon8"
>
> My cat /etc/mail/aliases
> # Basic system aliases -- these MUST be present.
> MAILER-DAEMON:      postmaster
> postmaster:         root
>
> # General redirections for pseudo accounts.
> adm:                root
> bin:                root
> daemon:             root
> exim:               root
> lp:                 root
> mail:               root
> named:              root
> nobody:             root
> postfix:            root
>
> # Well-known aliases -- these should be filled in!
> root:   syscon8@gmail.com
> fd:   syscon8@gmail.com
> # operator:
>
> # Standard RFC2142 aliases
> abuse:              postmaster
> ftp:                root
> hostmaster:         root
> news:               usenet
> noc:                root
> security:           root
> usenet:             root
> uucp:               root
> webmaster:          root
> www:                webmaster

You can grep your postfix files for root and root@ to find the culprit.  It
seems your postfix configuration is rewriting the 'Send As' name, if not whole
address.  My Postfix knowledge is rather out of date, but current users should
be able to advise with a specific fix for this problem.