How to detect forged From and Reply-to addresses from your own domain

Julian Field MailScanner at
Mon Mar 8 09:49:33 GMT 2010

On 08/03/2010 09:01, Anthony Cartmell wrote:
>> My ISP redirects all port 25 connects to its own servers so even if I
>> know what I'm doing, I can't use your MTA for my outgoing mail for this
>> account.
> I always instruct that they use the proper message submission port, 
> 587, for sending mail. This requires authentication so can be used 
> from anywhere on the internet without needing to change the outgoing 
> servername, and also works around any ISP that hijacks port 25.
I have found (through extensive travelling on the part of other staff 
here) that some hotel networks block everything except 80 (which they 
proxy) and 443. So I also provide SMTPS on 443 on our SMTP server, and 
IMAPS on 443 on our IMAP server. That way they can always reach their 
mail, I've never found anywhere (recently) that blocks 443.


Julian Field MEng CITP CEng
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