Although it is necessary and good practice to inform customers whose
work may be affected about changes and the schedule for implementation,
you must take care not to flood your customers with too many messages. If
you do, the customers will ignore them, thinking them irrelevant. Targeting
the correct groups for each service requires understanding your customer base
and your services in order to make appropriate mappings. For example, if
you know that group A uses services A to K and that group B uses services
B, D, and L to P, you need to let only group A know about changes to service
A, but you should let both groups, A and B, know about modifications to
service B. This task may seem tedious, but when it is done well, it makes a
huge difference to your customers.