Mails in Mac go straight to archive or trash


New Email

i've got a rather annoying problem i can't seem to fix and the more i look into it, the more confused i get. (Why are mail settings so damn medieval??!!!)

For a client of mine i've set up a new mailaccount (with the same emailaddress she had before) but on a new host. I used the host's MX settings to get the mail directed to her mailbox. She primarily uses mac's to recieve those mails, but she ocassionally also reads them into gmail (which is a google apps account).
She wants the 2 clients to recieve the mails in sync.

In i've set up an IMAP account (incoming IMAP/port 993 - outgoing SMTP/port 465) with SSL connection, for Google Apps i've entered Google's server settings on the hostside.
I've actually set up an account in her but also mine, for testing.

Mails are coming into the but immediately get sent to Archive of Trash folder. I've read online that this has happened also to others but i can't seem to find the exact solution to it. Furthermore, what is strange is that it happens both in my as well as her, which leads me to think it might be a server setting issue.

She uses MAC OSX 10.7, i use 10.9.

Is there anyone who might lead me to a solution? Any tip will do because i'm getting quite desparate.