You can no longer access your webmail application.

The URL to access webmail has changed. Rather than mydomain.com/up, use webmail.mydomain.com.

Cannot receive mail through an external email server, exchange/postini etc.

Note: May happen when hosting mail with another provider.

You will need the MX host or IP address of the external exchange mail server.  If not known, then Apollo techs can retrieve this info from /root/named.backup on ns.apollohosting.com.  Please contact an Apollo tech on our chat line with this question.

Once you know the IP/MX host it can be added through the plesk control panel, under the DNS icon.
you will need to do 1 of 2 things, if you know the MX host, change the MX record to point to mx.domain.com. 
If you know the ip change the A record for mail.theirdomain.com to point to this new IP.
There have also been some issues with the MX records reverting after being changed just in plesk, so Apollo techs have been updating the DNS on ns.apollohosting.com as well just to make sure.  Please send this request via chat to our tech staff.

Not receiving email notifications

Verify that the correct mail server is set. Log into your Miva Merchant Control Panel and go into the Domain settings. Set the Mail Server to 'localhost' instead of 'mail.domain.com'.

Broken store URLs

If you are able to login to the admin.mvc, check/fix URLs in the Domain Settings. If you are not, copy the domain.dbf from the ALA server's htsdata directory, replacing the current copy (after backing it up). Then login to admin.mvc, and change the secure URLs to the new Plesk values.

Email client (Outlook or others) can not POP your email account.  Comes back asking for login credentials.

Please change the user id for the particular email account to myname@mydomain.com instead of before where you only needed myname.