Roundcube disable multiple identities

Edit

config/main.inc.php

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// Set identities access level:
// 0 - many identities with possibility to edit all params
// 1 - many identities with possibility to edit all params but not email address
// 2 - one identity with possibility to edit all params
// 3 - one identity with possibility to edit all params but not email address
$rcmail_config['identities_level'] = 3;

Setting value of identities_level disallow users to change from email address.

See Roundcube