On 3/2/2017 the Zen Cart development team released version 1.5.5E.

Bugfix and a few other improvements:

• Fix bug introduced in v1.5.5c related to deleting customers
• Upgrade PHPMailer from 5.2.21 to 5.2.22
• Update gmail support to use TLS per published standards
• Add built-in support for new .htaccess rules required for Apache 2.4, so mod_compat doesn’t need to be installed
• zc_install improvements better handling for upgrades from v138 / v139
• zc_install – removed extraneous backticks from upgrade SQL from v154-to-v155
• Bridge compatibility for transition to removal of the ENABLE_SSL_ADMIN constant
• Consolidate to a single upload class, shared between admin/catalog
• Updates to Payeezy and First Data HCO payment mod