Space mail account is not visible via the UI although the data exist in the database after upgrading to 4.2.1

From <confluence-url>/mail/archive/viewmailaccounts.action?key=<space-key>, you'll see only the following remarks instead of an existing space mail account:

No POP accounts have been configured for this space. (Add Mail Account)

However, the space email configuration exist in the database (BANDANA table). You can run the following query to double check:

SELECT * FROM BANDANA where BANDANAKEY='atlassian.confluence.space.mailaccounts';

Further digging on this issue, it seems that in 4.0.3, IMAPS configration is as follows:

<list>
<imapMailAccount>
<id>1</id>
<name>Test</name>
<description>Test IMAP</description>
<hostname>atlassian.com</hostname>
<username>test@atlassian.com</username>
<password>check</password>
<port>993</port>
<secure>true</secure>
<status>true</status>
<enabled>true</enabled>
</imapMailAccount>
</list>

I made a comparison by creating a new mail space account in 4.2.1 and the data stored in the database looks like this:

<list>
  <com.atlassian.confluence.mail.archive.ImapMailAccount>
    <id>1</id>
    <name>Test</name>
    <description>Test IMAP</description>
    <hostname>atlassian.com</hostname>
    <username>test@atlassian.com</username>
    <password>check</password>
    <port>993</port>
    <secure>true</secure>
    <status>false</status>
    <enabled>true</enabled>
  </com.atlassian.confluence.mail.archive.ImapMailAccount>
</list>

The obvious difference that I could see and compare is the following tag:

<com.atlassian.confluence.mail.archive.ImapMailAccount>

instead of

<imapMailAccount> 

Workaround:

1. Grab the bandanavalue from this query:

   SELECT * FROM BANDANA where BANDANAKEY='atlassian.confluence.space.mailaccounts';
   

2. Copy that value to a text file, and change <imapMailAccount> to <com.atlassian.confluence.mail.archive.ImapMailAccount>
3. Insert it back into bandana with a query like this (replace the text between the ' characters with your own value from the step above:

   update BANDANA set BANDANAVALUE='<list>
     <com.atlassian.confluence.mail.archive.ImapMailAccount>
       <id>1</id>
       <name>Test</name>
       <description>Test IMAP</description>
       <hostname>atlassian.com</hostname>
       <username>test@atlassian.com</username>
       <password>check</password>
       <port>993</port>
       <secure>true</secure>
       <status>true</status>
       <enabled>true</enabled>
     </com.atlassian.confluence.mail.archive.ImapMailAccount>
   </list>'
   where BANDANAKEY='atlassian.confluence.space.mailaccounts';

4. Restart Confluence
5. The result is the space mail account is now visible and accessible from the page.