Slow email retrieval on only 1 account?

We have managed hosting for our small business, and pay for cPanel. This morning, one of our POP accounts (mine) was unable to retrieve mail. I can send mail through it. But retrieving either stalls completely, or is extremely slow, especially on any email with attachments.

I had an admin friend check the server and he said a log showed the following error:

Code:

cphulkd rejected registration attempt for dovecot with: 400 Unable to connect to database backend: Failed to connect to mysql db

I called our host, who ran me through the process of flushing the cphulk blacklist. However, the problem still exists. He was unable to help me further and said he'd escalate my issue, but suggested I post here.

FWIW, I am using Outlook for Mac 2011, but every other account I have set up works fine. I have tried deleting the account in Outlook, rebuilding the Outlook database, even deleting the POP account in cPanel and recreating it. Nothing works.

Please help?

 

According to my admin, that's where he found the cPHulk error. Nothing else looked out of the ordinary.

Late last night, after running some tests, this issue seemed to be affecting all POP accounts on this server, not just mine. We'd send a 3MB PDF attachment from a Gmail account to various POP accounts on our domain, as well as my personal email account, and attempt to retrieve them simultaneously. My personal account (Charter.net) would download the file instantly, whereas all the accounts on our domain would struggle or time out.

I was able to replicate this on 3 different setups: an iMac with Outlook for Mac 2011, a PC running Windows 7 using Live Mail, and an iPhone using Mail app. Same sluggish results on all 3 devices, for any email with an attachment. But plain text emails would download just fine.

Thoughts?