{"id":4581,"date":"2025-07-10T08:57:42","date_gmt":"2025-07-10T08:57:42","guid":{"rendered":"https:\/\/geekmungus.co.uk\/?p=4581"},"modified":"2025-07-10T08:57:44","modified_gmt":"2025-07-10T08:57:44","slug":"testing-smtps-from-command-line-with-authentication","status":"publish","type":"post","link":"https:\/\/geekmungus.co.uk\/?p=4581","title":{"rendered":"Testing SMTPS from Command Line (with Authentication)"},"content":{"rendered":"\n

Just like the testing of SMTP using Telnet, you can also perform the same steps if the target server is using TLS, however because telnet won’t do the job here, you can use OpenSSL instead. <\/p>\n\n\n\n

Here’s a simple example.<\/p>\n\n\n\n

Firstly get your Username and Password in Base64 format.<\/p>\n\n\n\n

echo -n \"username\" | base64\necho -n \"password\" | base64<\/code><\/pre>\n\n\n\n
You’ll get the Base64 encoded strings outputted after each command. Now you can make the connection and authenticate.<\/p>\n\n\n\n
Notice the -quiet at the end of the command, this is needed to ensure that if your username or password string contain “Q” it doesn’t just quit the command, see https:\/\/superuser.com\/questions\/1179522\/why-do-i-get-done-after-auth-login-command-to-smtp-server<\/a> for more details on this.<\/p>\n\n\n\n
openssl s_client -starttls smtp -crlf -connect mail.domain.com:587 -quiet\n\nehlo senderdomain.com\n\nauth login\n\nauth login\n334 VXNlcm5hbWU6\n<Base64 encoded username>\n334 UGFzc3dvcmQ6\n<Base64 encoded password>\n235 2.7.0 Authentication successful\n\nmail from:info@senderdomain.com\nrcpt to:info@domain.com\ndata\nTo:info@domain.com\nFrom:info@senderdomain.com\nSubject:A Test Message for You!\nHello,\nHow are you?\nThanks\nTristan\n.<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"
Just like the testing of SMTP using Telnet, you can also perform the same steps if the target server is using TLS, however because telnet won’t do the job here, you can use OpenSSL instead. Here’s a simple example. Firstly get your Username and Password in Base64 format. You’ll get the Base64 encoded strings outputted … Read more<\/a><\/p>\n","protected":false},"author":4,"featured_media":4439,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[20],"tags":[],"class_list":["post-4581","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-random"],"_links":{"self":[{"href":"https:\/\/geekmungus.co.uk\/index.php?rest_route=\/wp\/v2\/posts\/4581","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/geekmungus.co.uk\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/geekmungus.co.uk\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/geekmungus.co.uk\/index.php?rest_route=\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/geekmungus.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4581"}],"version-history":[{"count":1,"href":"https:\/\/geekmungus.co.uk\/index.php?rest_route=\/wp\/v2\/posts\/4581\/revisions"}],"predecessor-version":[{"id":4582,"href":"https:\/\/geekmungus.co.uk\/index.php?rest_route=\/wp\/v2\/posts\/4581\/revisions\/4582"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/geekmungus.co.uk\/index.php?rest_route=\/wp\/v2\/media\/4439"}],"wp:attachment":[{"href":"https:\/\/geekmungus.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4581"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/geekmungus.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4581"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/geekmungus.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4581"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}