connections from blackberry network not closing

[Alejandro P]

Hello, this connections comming from blackberry network are hanging the imap server, these connections seems to keep open all time, even if I close the port on the firewall they keep open.

This is a shared hosting server, so it is normal from my point of view to have multiple connections coming but the problem is they are not closing.

How can I limit the time connections stay open?

# netstat -plan |grep ESTAB |grep :993

netstat -plan |grep ESTAB |grep :993
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.70.81:50743 ESTABLISHED 16049/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.66.49:55379 ESTABLISHED 16256/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.68.227:46487 ESTABLISHED 16058/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.77.230:58003 ESTABLISHED 16214/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.70.43:55416 ESTABLISHED 16205/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.90.5:54829 ESTABLISHED 16078/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.68.193:52186 ESTABLISHED 16149/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.87.18:47589 ESTABLISHED 16104/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.78.135:37985 ESTABLISHED 16080/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.78.139:57963 ESTABLISHED 16290/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.87.106:37768 ESTABLISHED 16386/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.91.188:40800 ESTABLISHED 16277/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.84.15:54732 ESTABLISHED 16204/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.87.100:51878 ESTABLISHED 16307/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.70.121:43737 ESTABLISHED 16050/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.78.117:37587 ESTABLISHED 16227/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.87.218:59213 ESTABLISHED 16237/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.69.14:36491 ESTABLISHED 16213/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.86.215:41304 ESTABLISHED 16228/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.69.142:57366 ESTABLISHED 16098/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:68.171.237.45:40085 ESTABLISHED 16152/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.76.214:42428 ESTABLISHED 16095/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.68.172:32961 ESTABLISHED 14848/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.90.144:51414 ESTABLISHED 16236/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.65.197:35070 ESTABLISHED 16245/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.70.240:52718 ESTABLISHED 16055/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.91.177:38581 ESTABLISHED 16162/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.85.9:56058 ESTABLISHED 16084/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.65.157:57454 ESTABLISHED 16291/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.77.127:48770 ESTABLISHED 16159/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.64.214:41504 ESTABLISHED 16146/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.91.229:51211 ESTABLISHED 16094/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.79.255:50959 ESTABLISHED 16109/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.78.156:42095 ESTABLISHED 16119/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.78.156:42094 ESTABLISHED 16123/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.65.197:35072 ESTABLISHED 16246/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.64.214:41503 ESTABLISHED 16139/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.65.175:54113 ESTABLISHED 16189/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.67.27:46525 ESTABLISHED 16167/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.64.80:45055 ESTABLISHED 16105/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.65.181:49157 ESTABLISHED 16271/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.87.45:48000 ESTABLISHED 14703/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.79.63:41610 ESTABLISHED 16315/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.85.119:36571 ESTABLISHED 16088/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.70.66:58326 ESTABLISHED 16135/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.69.53:37800 ESTABLISHED 16388/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.85.211:57433 ESTABLISHED 16185/couriertls
tcp 0 0 ::ffff:174.36.xxx.xx:993 ::ffff:67.223.85.211:57432 ESTABLISHED 16168/couriertls

How do you handle this on your servers?
Do you allow connections to that port? How many of them stay alive along the day?

[Infopro]

In your WHM > Service Configuration > Mailserver Configuration, I think you'll find the settings you're looking for.

[Alejandro P]

In your WHM > Service Configuration > Mailserver Configuration, I think you'll find the settings you're looking for.

Hello Infopro, there are settings for manage the allowed number of concurrent connections, but no option to tell how to close inactive connections

In fact the problem is that open connections over that limit causes the service to stops responding

[Infopro]

In your log posted above you have 48 connections open by what appears to be a single IP using a blackberry. The default settings for this is 30 I believe.

Checking my own server with a Blackberry, iPhone and checking email from my home PC mail client connected via IMAP all at the same time, I show 3 connections for my IP with:
netstat -plan |grep ESTAB |grep :993

Instead of closing that port, I might consider blocking that IP instead and testing myself to be sure it's a server issue. If I connected to the server and started opening and not closing as many as 48 connections, I'd think it was a server problem. If I didn't, then something else is going on that might be a concern.

[cPanelDon]

For enhanced support of BlackBerry devices I would consider switching the IMAP/POP mail server from Courier to Dovecot. Dovecot has IMAP IDLE enabled by default and also supports the BlackBerry® FastMail Service; I believe these two features may offer improved performance for your users that connect from a BlackBerry or via BlackBerry Internet Service (BIS).

The IMAP/POP mail server can be toggled using WebHost Manager (WHM) via the following menu path (with linked documentation):
WHM: Main >> Service Configuration >> Mailserver Selection

After switching to Dovecot, you may locate usage information about BlackBerry® FastMail using cPanel via the following menu path:
cPanel: Main >> Mail >> Email Accounts >> BlackBerry® FastMail Service Enabled