{"id":119,"date":"2017-10-09T05:59:00","date_gmt":"2017-10-09T05:59:00","guid":{"rendered":"https:\/\/linuxadmin.melberi.com\/uncategorized\/disable-or-enable-open-relay-in"},"modified":"2017-10-09T10:46:09","modified_gmt":"2017-10-09T10:46:09","slug":"disable-or-enable-open-relay","status":"publish","type":"post","link":"https:\/\/www.melberi.com\/linuxadmin\/sendmail\/disable-or-enable-open-relay","title":{"rendered":"Disable or Enable open relay in Sendmail"},"content":{"rendered":"

How to Disable or Enable open relay in sendmail SMTP<\/p>\n

Sendmail Open relay<\/span><\/h2>\n

Open relay is disabled by default in Sendmail 8.9 and above.
\nIt will only allow relaying from localhost.
\nYou can edit the sendmail access database\u00a0 ( \/etc\/mail\/access) and enable or disable open relay.<\/p>\n

Default Configuration: <\/b><\/p>\n

#vim \/etc\/mail\/access<\/b><\/div>\n

Connect:localhost.localdomain\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 RELAY
Connect:localhost\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 RELAY
Connect:127.0.0.1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 RELAY<\/b><\/span>
\n
\n<\/b>
\nYou can use host name or ip address in the access database
\nyouordomain.com \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 RELAY <\/span><\/strong>
\n 10.5.10.5 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0 \u00a0 RELAY<\/span> <\/strong>
spam@buyme.com \u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 550 Spammers not allowed<\/span><\/strong>
virus@virusdomain.com\u00a0\u00a0\u00a0 DISCARD<\/span><\/strong><\/p>\n

<\/b>
\nTo Reject Mail Form Particular Host\/IP<\/b><\/p>\n

rejectserver.com\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 REJECT<\/b><\/span>
\n 10.10.2.2\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0 REJECT<\/b><\/span>
\n
\n<\/b><\/p>\n

Open Relay:<\/b><\/span><\/h3>\n

Open Relay servers will be configured to relay all ip range
\nBy adding the *.* entry in \/etc\/mail\/access you can enable relay for all<\/p>\n

*.*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 RELAY<\/b><\/div>\n

Also by adding your domain name in the \/etc\/mail\/relay-domains you can enable relay form particular domain server.
\nNow a days most of the mail servers will not allow mails from open relay servers.<\/p>\n

How to Disable Sendmail OPEN Relay<\/b><\/span><\/h3>\n

By allowing relay from only your local ip range and localhost, you can disable the open relay.
\n127.0.0.1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 RELAY<\/b>
\n192.168.1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 RELAY<\/b>
\nIf your server is configured with smtp auth or POP-before-SMTP<\/b>, then you can remove all the relay entries (Even local ip range) in the access database.
\nIt is always better to configure your server with smtp auth<\/b> or POP-before-SMTP<\/b> . This will be useful for roaming users also.<\/p>\n

Also check \/etc\/mail\/relay-domains and remove all the relay domains<\/p>\n

In some cases relaying is allowed even though it isn’t intended. This is because of the use of FEATURE(relay_entire_domain) which allows relaying for every system in class m. If class m is wrong, then the system may open up relaying for other hosts in that domain. You have to verify this
\necho ‘$=m’ | sendmail -bt -d0.4<\/b>
\nSometimes class m is set wrong to be just a TLD (e.g., com). In this case, fix your hostname to be host.sld.tld instead of sld.tld or change $m, or remove FEATURE(relay_entire_domain) and use other means instead<\/p>\n

Open Relay Testing Websites:<\/b><\/p>\n

http:\/\/www.abuse.net\/relay.html<\/a>
\nhttp:\/\/www.mob.net\/~ted\/tools\/relaytester.php3<\/a>
\nhttp:\/\/www.checkor.com\/<\/a><\/p>\n

MX Tool
\nhttp:\/\/www.mxtoolbox.com\/<\/a>
\nsmtp authentication vs. pop before smtp<\/a><\/b><\/p>\n

\u00a0<\/b><\/p>\n","protected":false},"excerpt":{"rendered":"

How to Disable or Enable open relay in sendmail SMTP Sendmail Open relay Open relay is disabled by default in Sendmail 8.9 and above. It will only allow relaying from… Read more »<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-119","post","type-post","status-publish","format-standard","hentry","category-sendmail"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t