Sometimes, it takes almost an hour late to receive or send a message. Never it’s right away. For important e-mail’s I have to acces my webmail, it’s really awfull to send or receive an urgent message 1 hour late.
Can you check that your send options are set correctly? Go to Menu > Tools > settings > Mail > Send. Send messages immediately should be checked.
For receiving, go to Menu > Tools > Settings > General, and make sure that sync is set to a reasonable time and is ticked. If this is set to 60 minutes, then you will only be receiving email once in an hour.
FYI, the “Synchronize items every XX minutes” is only relevant to POP3 accounts, IMAP servers push emails to the client (except for Comcast, of course), so you should receive them immediately regardless of this setting. Are you by chance using Comcast as your provider?
Of course you are correct Jay. I am so used to POP3 that I sometimes forget that IMAP works differently. 
Yeah, I knew you were a POP3 guy…
Jay, I was thinking of coming into the 21st century and moving to IMAP, but questions like Lucas posted above make me a little weary.
I have done some testing with IMAP inboxes having up to 3000 messages, and send/receive is not an issue. But when they get too big it seems that eM Client sometimes gets stuck for ages while syncing, and I am wondering how prolonged syncing effects send/receive.
Hi Gary:
For me, IMAP works flawlessly (approx. 6000 emails). IMAP is a must since I deal with multiple devices. I really don’t know why some people have slow send/receive and sync, but I have to believe it has something to do with their setup/machines or perhaps the provider.
My bandwidth is good at the office (75MB u/d) and pretty bad at home (12 d 1 u – I live in a rural area with few choices) and works just fine at both locations, so I don’t really think it is a bandwidth issue.
It could be a provider problem. I did try IMAP with a few free providers. Both GMail and Outlook.com were sluggish. Outlook.com was a little better though. GMX.com - no problem.
On a local IMAP server I also experience sync issues with large inboxes. So I agree, to a degree, bandwidth is irrelevant.