nullmailer – Diagnostic-Code: SMTP; 550 5.1.0 ＜root@external_email_server.com＞ sender rejected…

DevOps & SysAdmins: nullmailer – Diagnostic-Code: SMTP; 550 5.1.0 ＜root@external_email_server.com＞ sender rejected (497) Helpful? Please support me …

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by Roel Van de Paar

linux smtp server