Hmm seems like there may be 2 issues here. Delayed mail would indicate that rate-limiting has been triggered, usually due to spam concerns. That in itself should mean the system is working as intended but the delay time should not be excessive. If your emails have been delivered a substantial number of hours after being sent then I'd like to know so that I can investigate.
The other issue is the lack of expected mail. First thing I'd like you to do is the following please:
Access webmail and check your Spam settings are not set to Reject All Spam Messages.
Next check all folders in webmail, including Spam and Trash.
I have a couple of questions too:
Do you have an IOS device that accesses your emails?
Is your email setup as IMAP or POP?
Does anyone else have access to your emails that may have inadvertently deleted them?
Thanks for getting back to me with that information. Glad things have improved a little but would ask you to please read this post. It explains about some known issues with IOS devices deleting emails and I wonder if this might be a factor?
Slow delivery of mail is usually due to spam issues. However the delay should not be excessive, so please let me know what kind of delay you're experiencing and I'll see if that needs investigation.