Can not switch to SmarterMail or create mailbox - Failed to log in.

Symptoms

The following error is thrown upon attempt to switch from MailEnable to SmarterMail:

Error: Unable to set SmarterMail Server 10.7.4787 as the default Mail Server: defpackagemng failed: Execute mchk.exe failed with error code 1: Can't obtain mail box forwarding info.
Domain: domain.tld [domain.tld].
Mail name: sales.
Reason: Failed to log in
 ....
 (Error code 1)

The following error is thrown upon attempt to create mailbox:

Error: Unable to update the mail account properties:mailmng failed: Can't open domain.
Domain: domain.tld [domain.tld].
Reason: Failed to log in.
....
(Error code 1)

Cause

Integration between Plesk and Smartermail is broken.

Resolution

1. Ensure that no other services are listening on the 9998 port:

   "%windir%\\System32\\inetsrv\\appcmd" list site | findstr 9998
   SITE "Smartermail" (id:12,bindings:http/*:9998:,state:Started)
   SITE "webmail(SmarterMail)" (id:13,bindings:http/192.168.0.67:9998:,state:Started)
   

2. Remove the 9998 port from other website's bindings in IIS. In the example above it is webmail(SmarterMail).

3. Ensure that correct login and password are set on the Home > Tools & Settings > Plesk Components > SmarterMail Server page.

4. Reset password for SmarterMail if necessary. Refer to the following article on how to reset password - How to reset password for SmarterMail