imap, multiple domains and many questions

[websrvr]

I know very little about imap and find the manual confising as hell  
but I'm having an issue that I don't even know if I can explain  
properly but I'm looking for a solution.

I have local users and virtual users (virtual users are stored in  
mysql) and In postfix these virtual users are using  
'virtual_mailbox_base = /var/mail/vhosts" as defined in main.cf and  
local users mail is '/var/imap'.

How do I get imap to recognize which user is local and which is virtual?



How do I get imap to have a different servername based on the IP it's  
called on so I can use "%u@%r" to authenticate these users?
(the server has several IP's assigned to it.)



How do I get imap to accept '@domain.tld' as part of the username,  
currently, it seems to not want to authenticate a user when they have  
their domain as part of their username.
ex. "derrick at mustangrestomods.com' wont authenticate, here is the log  
on the attempt to authenticate to retrieve e-mail.
May 22 00:12:28 dellc imap[21648]: accepted connection
May 22 00:12:28 dellc imap[21648]: badlogin:  
relay.mustangrestomods.com [67.78.11.226] CRAM-MD5 [SASL(-13):  
authentication failure: bad userid authenticated]
May 22 00:12:41 dellc imap[21648]: badlogin:  
relay.mustangrestomods.com [67.78.11.226] CRAM-MD5 [SASL(-13):  
authentication failure: bad userid authenticated]



I have the following entries in imapd.conf but don't know if they're  
doing anything or set right?
virtdomains: userid
sharedprefix: Teamordner
userprefix: Accounts
unix_group_enable: 0
autocreatequota: -1
partition-virtual: /private/var/mail/vhosts


Here is the actual imapd.conf file in case information is required  
that I have not provided.

configdirectory: /var/imap
partition-default: /var/spool/imap
sievedir: /usr/sieve
servername: daleenterprise.com
admins: cyrusimap
unixhierarchysep: yes
altnamespace: yes
sendmail: /usr/sbin/sendmail
lmtp_downcase_rcpt: 0
tls_cert_file: /etc/certificates/Default.crt
tls_key_file: /etc/certificates/Default.key
log_rolling_days: 7
log_rolling_days_enabled: false
sasl_auxprop_plugin: sql
sasl_sql_engine: mysql
sasl_allowanonymouslogin: no
sasl_allowplaintext: yes
sasl_mech_list: PLAIN LOGIN CRAM-MD5 DIGEST-MD5 NTLM
sasl_sql_user: pfix
sasl_sql_passwd: pfix
sasl_sql_hostnames: localhost
sasl_sql_database: pfix
sasl_sql_select: SELECT password FROM mailbox WHERE name = '%u' AND  
active='1'
sasl_sql_verbose: yes
virtdomains: userid
sharedprefix: Teamordner
userprefix: Accounts
unix_group_enable: 0
autocreatequota: -1
#reject8bit: 0
timeout: 60
username_tolower: 1
annotation_db: skiplist
duplicate_db: berkeley-nosync
mboxlist_db: skiplist
ptscache_db: berkeley
seenstate_db: skiplist
subscription_db: flat
partition-virtual: /private/var/mail/vhosts