Lingering mailboxes means that Mercury will keep a copy of the mailbox image in RAM for a specified amount of time in case the IMAP clients connects again. It's mainly useful if you use a webmail program or some other IMAP client with limited cache functions.

It should be safe to increase the value to 600 as long as you have sufficient free RAM to handle it. Around 300 KB per mailbox is required.

It's been suggested that mixing POP3 access with having lingering mailboxes could cause problems. I haven't tested that myself so I can't say if there is a risk with it - maybe someone else has more information.

/Rolf 

What to consider (positive and negative), if I want to increase linger timeout value from 60 to say, 300 or 600?

Typical use of our users are:
1. Only use Webmail SquirellMail, never POP3 or IMAP mail client.
2. Use Webmail for quick check emails, such as check for big attachment and remove them if not important. Then exit Webmail and retrieve rest of emails using POP3 mail client.
3. Users do not use Pegasus.

Thanks in advance.