10-11-2026, 12:14 PM
Test sending and receiving separately. A message in Sent means the client submitted it; it does not prove delivery to an external user's Inbox.
Lab evidence: Roundcube submitted a message from [email protected] to the same lab mailbox, and it appeared in Inbox. A separate outbound message was accepted by SEOStackTools Email Tester and scored 95/100 (Grade A), with SPF, DKIM, DMARC and PTR passing. External inbound delivery from another provider has not yet been verified in this lab.
1. Check the setup before sending
You need an enabled mailbox, correct MX/A records, running Postfix and Dovecot, trusted mail TLS and working webmail or a configured email client. For external delivery, the provider must allow outbound SMTP traffic. PTR and sender reputation also affect acceptance.
Sign into your HTTPS webmail address with the full mailbox address and mailbox password. Our lab uses webmail.adminslab.com.
2. Compose a simple test
1. Click Compose in Roundcube's left menu.
2. Check From is your mailbox.
3. Enter a recipient address you control in To and press Enter so it becomes a recipient entry.
4. Enter a unique Subject, for example Mail test 01.
5. Enter a short normal message in Message Body.
6. Leave Save sent message in set to Sent.
7. Click Send once and wait for the result.
For an initial local test, send to your own lab mailbox. This checks submission and local storage without depending on another provider. Then repeat with an external address you control.
3. Check Sent and the destination
Open Sent and locate the unique subject. At the receiving account, check Inbox and Spam/Junk. If it arrives, reply from that external account to your aaPanel mailbox. This return message tests external inbound delivery.
In Roundcube, open Inbox and click Refresh. Open the received message and use Reply for a normal conversation test. Record which direction succeeds; avoid calling the whole setup verified when only one direction was tested.
4. Use a desktop client if required
Get your mailbox's connection details from Mail Server → Mailboxes → Login info → Copy. For our verified TLS endpoints, the hostname is mail.adminslab.com, IMAP uses 993 with SSL/TLS, and authenticated SMTP uses 587 with STARTTLS. Use the full mailbox address as username. Confirm these values against your own server configuration rather than copying the lab hostname.
5. Diagnose a missing message
Next check: use SEOStackTools Email Tester to examine authentication and delivery deductions. Local receipt and an external 250 acceptance are useful evidence, but neither guarantees inbox placement at every provider.
Screenshot: working mailbox
![[Image: mail-webmail-branded-20261011.png]](https://adminsforum.com/uploads/tutorials/mail-webmail-branded-20261011.png)
Previous: Install and access webmail
Lab evidence: Roundcube submitted a message from [email protected] to the same lab mailbox, and it appeared in Inbox. A separate outbound message was accepted by SEOStackTools Email Tester and scored 95/100 (Grade A), with SPF, DKIM, DMARC and PTR passing. External inbound delivery from another provider has not yet been verified in this lab.
1. Check the setup before sending
You need an enabled mailbox, correct MX/A records, running Postfix and Dovecot, trusted mail TLS and working webmail or a configured email client. For external delivery, the provider must allow outbound SMTP traffic. PTR and sender reputation also affect acceptance.
Sign into your HTTPS webmail address with the full mailbox address and mailbox password. Our lab uses webmail.adminslab.com.
2. Compose a simple test
1. Click Compose in Roundcube's left menu.
2. Check From is your mailbox.
3. Enter a recipient address you control in To and press Enter so it becomes a recipient entry.
4. Enter a unique Subject, for example Mail test 01.
5. Enter a short normal message in Message Body.
6. Leave Save sent message in set to Sent.
7. Click Send once and wait for the result.
For an initial local test, send to your own lab mailbox. This checks submission and local storage without depending on another provider. Then repeat with an external address you control.
3. Check Sent and the destination
Open Sent and locate the unique subject. At the receiving account, check Inbox and Spam/Junk. If it arrives, reply from that external account to your aaPanel mailbox. This return message tests external inbound delivery.
In Roundcube, open Inbox and click Refresh. Open the received message and use Reply for a normal conversation test. Record which direction succeeds; avoid calling the whole setup verified when only one direction was tested.
4. Use a desktop client if required
Get your mailbox's connection details from Mail Server → Mailboxes → Login info → Copy. For our verified TLS endpoints, the hostname is mail.adminslab.com, IMAP uses 993 with SSL/TLS, and authenticated SMTP uses 587 with STARTTLS. Use the full mailbox address as username. Confirm these values against your own server configuration rather than copying the lab hostname.
5. Diagnose a missing message
- Send fails immediately: read the exact client error; check authentication, SMTP service and connection settings.
- Sent exists but remote delivery fails: inspect Postfix queue/logs for the recipient, status and remote rejection reason. A queued message remains pending.
- Incoming mail never arrives: verify public MX, the MX target's A record, inbound port 25, provider firewall and recipient spelling.
- Mail reaches Junk: inspect SPF/DKIM/DMARC alignment, PTR, content and reputation. Do not keep resending identical messages rapidly.
Next check: use SEOStackTools Email Tester to examine authentication and delivery deductions. Local receipt and an external 250 acceptance are useful evidence, but neither guarantees inbox placement at every provider.
Screenshot: working mailbox
Previous: Install and access webmail