no, if it is clickable.

what i do is:
go to the domain, click to the "enable Relay without verifying local recipients on a domain" checkbox and save.

if i then go again to this domain i see thet the "enable Relay without verifying local recipients on a domain" checbox is not marked, so could click it again... .when i go wan page back i see then tat the "backupmx box is checked".

i can then disable the backupmx box again but this means that the value of the "enable Relay without verifying local recipients on a domain" checkbox must be wrong som how...

GaXy

now i can click on the  "enable Relay without verifying local recipients on a domain" checkbox and save but nothing happen.

after checking, the checkbox is still not marked anymore...

hmmm i would say that this is not what i like to do or how i understand it:

i am under the domain settings-->relay

Relay/Transport Setting : here i have dovecot, ok

Description on the right:
Received emails will be relayed to specified server.
Per-user relay setting will override per-domain relay setting you set in this page.

but there is also a checkbox:
Relay without verifying local recipients

and if i click to that box, it is never saved.

I don't quite understand what you really want/expect.

If you want to perform smtp authentication as 'relay@domain.abc', but make the email looks like sent by 'some_other_user@', you can simply remove 'reject_sender_login_mismatch' in Postfix, then update setting in your mail client application to achieve this.

If this is what you want, then 'relay' is not what you're looking for.