5. Sending mail from outside Oxford

This section relates to sending mail from outside Oxford to oxmail in its mail exchanger role.

Mail to postmaster@ox.ac.uk and abuse@ox.ac.uk bypasses most checks in order to allow queries about problems.

DNS-based blacklists

The following DNSBLs are used

NameZoneWeb
MAPS RBL+ rbl-plus.mail-abuse.ja.net http://www.mail-abuse.com/
PSBL psbl.surriel.com http://psbl.org/
Spamcop bl.spamcop.net http://spamcop.net/
Spamhaus ZEN zen.dnsbl.ja.net http://www.spamhaus.org/zen/

Mail coming from a server listed in one of these DNSBLs won't be rejected. It will attract a weighting in the SpamAssassin scoring and also experience small delays in response to some SMTP commands.

HELO/EHLO

Mail transactions must start with HELO.

The HELO argument must be syntactically correct. See RFC1123 section 5.2.5 and RFC5321 section 4.1.1.1 for guidance on choosing your HELO argument. A common mistake is to use the underscore character; this is not allowed.

MAIL FROM

The envelope sender must be valid and accept error messages (aka bounces). A common mistake is to send mail from a script without thinking about the sender address e.g. apache@foo.example.com . If there's neither an MX record for nor an MTA on foo.example.com then the sender address will be invalid.

RCPT TO

No recipient local-part may contain any of the following characters @ ! % / | "

The maximum number of recipients allowed for one message is 500. Excess recipients are temporarily rejected.

DATA

The maximum message size is 100 Mbytes.

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