If you want help with this query, why not post it in human-readable form?
eg ...
SELECT
vtiger_contactscf.cf_632, vtiger_contactdetails.firstname, vtiger_contactdetails.lastname,
vtiger_contactscf.cf_1425, vtiger_contactdetails.email, vtiger_contactscf.cf_630,
vtiger_contactscf.cf_634, vtiger_contactdetails.mobile, vtiger_contactscf.cf_744,
vtiger_contactdetails.contactid, vtiger_crmentity_user_field.starred
FROM vtiger_contactdetails
JOIN vtiger_crmentity ON vtiger_contactdetails.contactid = vtiger_crmentity.crmid
JOIN vtiger_contactscf ON vtiger_contactdetails.contactid =
vtiger_contactscf.contactid
LEFT JOIN vtiger_crmentity_user_field ON vtiger_contactdetails.contactid =
vtiger_crmentity_user_field.recordid
AND vtiger_crmentity_user_field.userid=N
LEFT JOIN vtiger_users ON vtiger_crmentity.smownerid = vtiger_users.id
LEFT JOIN vtiger_groups ON vtiger_crmentity.smownerid = vtiger_groups.groupid
WHERE vtiger_crmentity.deleted=N
AND ( (( (trim(CONCAT(vtiger_users.first_name,'S',vtiger_users.last_name)) = 'S'
or vtiger_groups.groupname = 'S')) )
)
AND vtiger_contactdetails.contactid > N ORDER BY vtiger_crmentity.modifiedtime DESC LIMIT N,N ;
\
"N" is an undefined value. The query can't run till N is replaced by a value or by a reference supplied in the query.
So you'll need to fix that, then run Explain on it. If you need help turning that result into optimisations, please post the Explain result here inside
BBCode code tags, and also post the Show Create Table results for each table, plus the value of innodb_buffer_pool_size.