Stopping following spam case

[Alexander]

I noticed that spammers send Mail via Port 25 to local email boxes using the recipient address as sending address. Is there a way to add a block, so that it's not possible to use port 25 to send mail to a recipient using his address as sender address.

Example: [e-mail] to [e-mail] should be blocked as spam.

[S B]

What if you email yourself things so you can have it on a tablet or webmail? - I do this often

It would also stop test messages in Microsoft Outlook working

[Alexander]

This case would go via transmission port 587 and you would authenticate to send mail via your server, so no problem at all.

[Alexander]

Actually, it should be extended to the following: Mails with a locally hosted domain in the sender adress that are sent via another mail server should be blocked unless the sending server is whitlisted.

[Roman]

I think this can be solved with SPF/DKIM

[Scott MacDonald]

The second case/example yes.. but I'm not sure about the 1st. SPF, when used strict can certainly reduce SPAM.

Are you using SPF Alexander?

[Alexander]

yes, I use SPF, DKIM and DMARC

[SH]

I must close this, there is nothing I can do about it if we don't want break delivery in some edge cases. If you filter out messages which has From header matching your local domain you will loose ability to use multiple smtp/delivery servers. Also group messaging migh be broken too.

But some filtration can be done, see #503