Looking for logging into the 250 Auth Plain site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the 250 Auth Plain site. After that you can login as usual with your login credentials.
http://www.google.co.jp/url?url=http://www.turbolinux.com/products/server/10s/manual/user_guide/user_guide/x4202.html
https://hogem.hatenablog.com/entry/20100121/1264179124
https://www.itmedia.co.jp/help/howto/security/special10/04.html
https://qiita.com/azumakuniyuki/items/99c341e99a459d6214bc
http://www.google.co.jp/url?url=http://www.samlogic.net/articles/smtp-commands-reference-auth.htm
http://www.google.co.jp/url?url=http://www.tohoho-web.com/ex/draft/smtp-auth.htm
http://www.google.co.jp/url?url=http://blog.h2onda.net/post/22651567480/noencryption-smtp-auth
https://de.wikipedia.org/wiki/SMTP-Auth
https://fsck.jp/%3Fp%3D808
https://support.plesk.com/hc/ja/articles/213360809--SMTP-%25E8%25AA%258D%25E8%25A8%25BC%25E3%2581%258CSMTP-%25E3%2582%25A8%25E3%2583%25A9%25E3%2583%25BC-250-Authentication-failed-%25E3%2581%25A7%25E5%25A4%25B1%25E6%2595%2597%25E3%2581%2597%25E3%2581%25BE%25E3%2581%2599
http://www.google.co.jp/url?url=http://www.aconus.com/~oyaji/mail2/smtp-auth-tst.htm
https://stackoverflow.com/questions/42852748/whats-different-between-250-auth-login-plain-and-250-auth-login-plain
https://www.ndchost.com/wiki/mail/test-smtp-auth-telnet