I had a task to migrate email accounts from cPanel to Siteground and when I tried using the Horde interface to export each folder it kept timing out

A tool called Maildir Converter did the job great however it only does 25 messages at a time on the free version so be aware of that limitation

Using Filezilla I connected to cPanel with SFTP and went to the following location:

/home/accountname/mail/example.com/chris

On the left side of Filezilla I created a folder called RAW and inside there I created a folder for each folder I wanted to export (Inbox, Sent, Archive, Ect.)

On the right side for Inbox go into the folder called cur and you should see several files which relate to your email messages

Copy them to where they need to be then repeat the steps for any other folders you want to export (.Sent/cur, .Archive/cur, ect.)

Open SysToold Maildir Converter and select the folder you want to convert and click Export

Select a location to output which I normally select the root of the user (e.g /EmailMigrationArchive/Chris) then export to MBOX then click Export

Do that for each folder you want to convert (A save report message comes up each time which I don’t need so I cancel it)

Go to the folder and you will see your converted messages which I like to compress into a zip archive

Then it can be used to import into a large variety of supported platforms

 

References:

https://www.systoolsgroup.com/updates/horde-email-export-not-working/
https://www.liquidweb.com/kb/export-emails-webmail-cpanel-server/