I'm not sure where to bring this information and any help would be most appreciated.
I have noticed that yahoo mail is using SMTP and not ESMTP. This is quite an issue in bandwidth saving as now the size limit for mail on yahoo is 10MB if I'm not mistaken. In many places in the world we limit our e-mail size to 2MB or less. By having yahoo to use SMTP our servers are obliged to receive the whole 10MB before the mailer can reply back size too big.
This is also an issue that could be brought to the SMTP group, to know if you can stop the Data stream to reply an error message, as you may know from the beginning of the data stream you will not accept the e-mail. For instance I also check the body early to see if it has not any forbidden attachment. I think the moment the protocol states that you have to wait for the .<CR><LF> in the DATA to reply back with an error message?
Finally is it feasible to refuse mail from SMTP mailers only? What the standards are saying?
Here are some packet capture. Gmail and hotmail follows ESMTP but yahoo follows SMTP.
220 cobalt.sopac.org.fj ESMTP Postfix.
EHLO mproxy.gmail.com.
250-cobalt.sopac.org.fj.
250-PIPELINING.
250-SIZE 1500000.
250-VRFY.
250-ETRN.
250 8BITMIME.
220 cobalt.sopac.org.fj ESMTP Postfix.
EHLO bay0-pcs1.bay0.hotmail.com.
250-cobalt.sopac.org.fj.
250-PIPELINING.
250-SIZE 1500000.
250-VRFY.
250-ETRN.
250 8BITMIME.
MAIL From:<abuse@xxxxxxxxxxx> SIZE=946.
220 cobalt.sopac.org.fj ESMTP Postfix.
HELO web8407.mail.in.yahoo.com.
250 cobalt.sopac.org.fj.
Thanks all for helping us in the Pacific Islands to save our costly bandwidth.
Cheers
Franck Martin
Vice-Chair PICISOC (Pacific Islands Chapter of the Internet Society)
www.picisoc.org
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