title: Exchange Server 2019: "550 5.7.60 SMTP; Client does not have permissions to send as this sender" on selected users
body: <p>I have an Exchange Server 2019 on premises working as our mail company server.
  Some users can't (others can) send mails via SMPT port 25. Is not an Open relay, the problem was sending internal an external destinations.</p>
  <p>This is the result from smtp test at <a href="https://www.gmass.co/smtp-test" rel="nofollow noreferrer">https://www.gmass.co/smtp-test</a></p>
  <pre><code>220 mail.mydomain.com Microsoft ESMTP MAIL Service ready at Tue, 13 Sep 2022 21:09:25 ?
  EHLO [172.31.1.116]
  250-mail.mydomain.com Hello [xxx.xxx.xxx.xxx]
  250-SIZE 37748736
  250-PIPELINING
  250-DSN
  250-ENHANCEDSTATUSCODES
  250-AUTH LOGIN
  250-8BITMIME
  250-BINARYMIME
  250-CHUNKING
  250 SMTPUTF8
  AUTH LOGIN
  334 [xxx]
  [xxx]
  334 [xxx]
  [xxx]
  235 2.7.0 Authentication successful
  MAIL FROM:&lt;myuser@mydomain.com&gt; SIZE=554
  RCPT TO:&lt;anotheruser@mydomain.com&gt;
  250 2.1.0 Sender OK
  250 2.1.5 Recipient OK
  DATA
  354 Start mail input; end with &lt;CRLF&gt;.&lt;CRLF&gt;
  From: myuser@mydomain.com
  Date: Tue, 13 Sep 2022 19:09:19 ?
  Subject: SMTP test from mail.mydomain.com
  Message-Id: &lt;507S7CPHVHU4.D86IGJWU6VG32@WIN-AUIR3RRGP88&gt;
  To: anotheruser@mydomain.com
  MIME-Version: 1.0
  Content-Type: multipart/alternative; boundary=&quot;=-It6fjVK5MLh5hmyoGNPCPg==&quot;
  --=-It6fjVK5MLh5hmyoGNPCPg==
  Content-Type: text/plain; charset=utf-8
  Test message
  --=-It6fjVK5MLh5hmyoGNPCPg==
  Content-Type: text/html; charset=utf-8
  Content-Id: &lt;507S7CPHVHU4.5IUQIQGPZEUA2@WIN-AUIR3RRGP88&gt;
  &lt;b&gt;Test message&lt;/b&gt;
  --=-It6fjVK5MLh5hmyoGNPCPg==--
  .
  **550 5.7.60 SMTP; Client does not have permissions to send as this sender**
  RSET
  250 2.0.0 Resetting
  </code></pre>
  <p>But with other users the result is:</p>
  <pre><code>250 2.6.0 &lt;WB6MM4SHVHU4.ZVXOEXV0CG8U@WIN-AUIR3RRGP88&gt; [InternalId=62423054680070, Hostname=myhostname] 1618 bytes in 0.332, 4,754 KB/sec Queued mail for delivery
  </code></pre>
  <p>I have tried deleting the user, recreating it and reassigning the mailbox, but it doesn't work.</p>
  <p>Any idea?
  Thanks for your time!</p>