Mobile User Configuration Guide

Most organizations, in the effort of controlling SPAM from being sent out of their private network, do prevent user from accessing the SMTP server port 25 directly. To support customers with SMTP access requirements from a non-fixed location, especially from private network with such policies, the following additional ports are available.

additional port 465, 587

465 => SSL/TLS on connect immediately required

587 => startTLS/Auto (recommended for outlook and thunderbird clients)

25 => start TLS optional (not recommended unless you cannot use 465 or 587) Customers are reminded to enable SSL/TLS encryption authentication even for port 25 even though it is not strictly required.