Error maildrop already locked

Email user in my office complaint because she could not download email from MDaemon server. Error message in outlook is:

Task '192.168.0.25 - Sending and Receiving' reported error (0x800CCC92) : 'Your e-mail server rejected your login. Verify your user name and password in your account properties. Under Tools, click E-mail accounts. The server responded: -ERR access denied'

After changing user password end retry to send and receive again this error is still occur. And then I check log mail POP in MDaemon server. The log status is fail with this error message in log file:

Thu 2010-07-01 08:11:17: Session 1437; child 4
Thu 2010-07-01 08:11:15: Accepting POP connection from [172.19.5.31 : 1062]
Thu 2010-07-01 08:11:15: --> +OK mydomain.com POP MDaemon 9.0.6 ready
Thu 2010-07-01 08:11:16: <-- USER john Thu 2010-07-01 08:11:16: --> +OK john... User ok
Thu 2010-07-01 08:11:17: <-- PASS ****** Thu 2010-07-01 08:11:17: --> -ERR maildrop already locked
Thu 2010-07-01 08:11:17: POP session terminated, (Bytes in/out: 20/145)

Then I check the mail box of the user and I found there are more than 10 emails in user mail box. One of the email sizes is more than 8MB. I tried to delete this email but I could not delete because the email file was locked. To delete this email I must restart MDaemon server first.

Mail Rejected by Keyword

I received complaint from user that her mail was rejected by the receiver mail server.

The massages from mail server are:

Subject: Undelivered Mail Returned to Sender
This is the mail system at host mxwcom.263xmail.com.
I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report.
You can delete your own text from the attached returned message.
The mail system
: host mxcom.263xmail.com[211.150.64.38] said:
mail rejected by keyword (in reply to end of DATA command)

Referring to that message I conclude that the content of email from the user contain keyword that is usually use by spam email. Then I checked the content of email and I found keyword "offering price" in the message.

I asked to the user to change keyword "offering price" in her email and resend the email to the recipient.

After changing "offering price" words with "quotation" and resending the email, then the email was sent successfully and no rejection from recipient email server.

Email sending error because of too many connections

There were many reason of email sending error. One of them is because of too many connections to the server. This is the sample MDaemon email server logs of sending mail failure because of too many connections to the mail server.

Sender user is: user@mycompany.com
Recipient user is: theuser@telkom.net

In this log there is line:

Fri 2010-03-12 07:41:33: <-- 421 #4.4.5 Too many connections to this host Fri 2010-03-12 07:41:33: --> QUIT
Fri 2010-03-12 07:41:33: Socket connection closed by the other side (how rude!)

This mean the recipient mail server could not receive email from user@mycompany.com because in the same time the server receipt too many connection (may be from other email server) that could not be handled.

MDaemon server (Sender user mail server) will automatically resend the mail from user@mycompany.com to theuser@telkom.net next time depend on the setting of MDaemon mail server.

Fri 2010-03-12 07:41:33: Session 8894; child 10
Fri 2010-03-12 07:41:31: Parsing Message
Fri 2010-03-12 07:41:31: From: user@mycompany.com
Fri 2010-03-12 07:41:31: To: theuser@telkom.net
Fri 2010-03-12 07:41:31: Subject: Kelebihan Pengobatan
Fri 2010-03-12 07:41:31: Message-ID:
Fri 2010-03-12 07:41:31: MX-record resolution of [telkom.net] in progress (DNS Server: 202.152.0.2)...
Fri 2010-03-12 07:41:31: * P=011 S=000 D=telkom.net TTL=(0) MX=[mx2.mail.plasa.com] {222.124.18.72}
Fri 2010-03-12 07:41:31: * P=011 S=001 D=telkom.net TTL=(0) MX=[mx1.mail.plasa.com] {222.124.18.71}
Fri 2010-03-12 07:41:31: Attempting MX: P=011 S=000 D=telkom.net TTL=(0) MX=[mx2.mail.plasa.com] {222.124.18.72}
Fri 2010-03-12 07:41:31: Attempting SMTP connection to [222.124.18.72 : 25]
Fri 2010-03-12 07:41:31: Waiting for connection...
Fri 2010-03-12 07:41:32: Connection established (192.168.0.25 : 2790 -> 222.124.18.72 : 25)
Fri 2010-03-12 07:41:32: Waiting for protocol initiation...
Fri 2010-03-12 07:41:32: <-- 421 #4.4.5 Too many connections to this host. Fri 2010-03-12 07:41:32: --> QUIT
Fri 2010-03-12 07:41:32: Attempting MX: P=011 S=001 D=telkom.net TTL=(0) MX=[mx1.mail.plasa.com] {222.124.18.71}
Fri 2010-03-12 07:41:32: Attempting SMTP connection to [222.124.18.71 : 25]
Fri 2010-03-12 07:41:32: Waiting for connection...
Fri 2010-03-12 07:41:32: Connection established (192.168.0.25 : 2798 -> 222.124.18.71 : 25)
Fri 2010-03-12 07:41:32: Waiting for protocol initiation...
Fri 2010-03-12 07:41:33: <-- 421 #4.4.5 Too many connections to this host. Fri 2010-03-12 07:41:33: --> QUIT
Fri 2010-03-12 07:41:33: Socket connection closed by the other side (how rude!)
Fri 2010-03-12 07:41:33: This message is 1 days old; it has 4 days left to get delivered
Fri 2010-03-12 07:41:33: SMTP session terminated (Bytes in/out: 94/12)