If your exchange password for the mailbox Access CRM uses has recently been changed it will also need updating in CRM. Please have an administrator follow these steps:
Go to the Admin menu
Under the Email, section click Group Mail Account
Click on the email used
Choose Edit
Select the Change your password link, and enter the new password
Press Save. You can also opt to Test Connection, to ensure the new password in working.
If the above is not the case, it is likely an email containing a large amount of images has had an archive attempt which will then run again and other emails will come through but the large email will fail, this is currently a system limitation.
If this is still not working as expected, please see the following Get support in Access CRM and reference the title of this article.