I am using vbulletin forum vb4.2.0
i got many times 508 resource limit reached error some time.
i have found one issue, i see in admin cp with Number of Queued E-Mails 1,008, and this query for birthday mail that i have identify, because the scheduled task with birthday email sending time as same.
issue: when the mail was generated for sending birthday, then there is 508 error comes. and its still available 20-30 mins. and my cpanel showing 30/30 EP
Now tell me which is configuration i need to increase, that will solve the problem?
Have you tried contacting your host to see what the problem is, it may not be the queued emails, if it is however then you CAN disable this feature, by going to AdminCP > Scheduled Tasks > Birthdays > Disable.
If you want to keep this task running however then consider upgrading your package or in fact another host if they have such a small limit on resources.
508 error most likely means that your are exceeding your resources - CPU, RAM, etc. Contact your in hosting and they will advise if update is required. However before that, check your error logs, for sure some information could be gathered.
As patrick said, it's processes. If it's not a cheap plan then your host might be willing to raise the maximum 30 processes.
It's worth noting that it's entry processes and not total processes.
You can spawn one process that has several children processes and still have it count as just one - in this case you could have a PHP script that runs for a while and sends numerous messages but only counts as one EP as well.
You either have a lot of stuff going on at once - various things - or vBulletin isn't coded very well for a shared environment - either is possible but I could only speculate without actually seeing your account.
Log into SSH and run "top" and then hit "u" and type your username or ask your provider for a list of processes at the time if they're responsive enough.
I remember having this issue at Bluehost (ages ago) and it ended up being imap that tied all the processes up. Something about the way a mac system handles the connections. As others have said, if you can't figure it out ask your host. They should be able to point you in the right direction.