See also the official documentation:
Help Center > Members Manual > Working with group messages > Reporting messages to moderators or to Groups.io support

Complaints About Messages

Circumstances may occasionally arise whereby a member of a group has, or believes they have, grounds to object to the contents of a message posted by another member. This wiki aims to set out how a complaint may be made, and what happens, and does not happen, as a result.

It must be noted that what follows applies only to members who use the web UI, because it is only the web UI that provides a specific Report This Message function. Members who wish to raise a complaint about a message received by email without using the web UI will have to communicate directly with the relevant Group Owner / Moderators by email in the hope of achieving a resolution. This wiki does not include any guidance about how to send emails back and forth.

To make things as simple as is possible, in what follows the person who sends a message to which someone else is going to object will be called the originator. The person who subsequently reports the message to lodge an objection will be called the complainant. It is not practicable to list what the grounds for any objection might be in this wiki, other than to determine which of two broad categories applies.

The Originator posts a message to a group, and another member is sufficiently unhappy about it that they wish to have it reviewed and perhaps removed. (Editing after posting may or not be available to individual members, and in any event may not involve sufficient censure, depending on the exact circumstances.)

The Complainant can report their concern as follows: beneath every message (again note this applies only to users of the web UI) there is a pale grey (gray) horizontal band with the options of Reply, Like, and More on it. Clicking on More reveals a pick list of options, one of which is Report This Message. (The pick list differs for members and moderators; the screenshot below is for a member. Both include Report This Message)

 Clicking on Report This Message brings up the Report Message template below:

The Note at the bottom means that your email address is included with the abuse report.

Any complaint has to fall into one or other of two broad categories; the first one (set by default) is for a complaint with which the Group Owner and Moderators can deal; the second is to send the report to Support at Groups.io because in the view of the complainant the message infringes the Terms of Service to which all Groups.io Account Holders are subject. If appropriate the complainant may select the second category simply by clicking on the circle beside Report to Groups.io Support.

Above this selection is a box into which the complainant must type the substance of their complaint. On completion of this the report must be submitted by clicking on the red Report tab.

At this point “what happens next” is a function of which type of complaint is being made.

For a complaint to the Owner / Moderators an email is sent to the Group Owner’s address reporting the fact that <member’s email address> has submitted a complaint about the message. A link to the reported message is included in the email.

The reported message remains in place on the web UI; the originator is not informed that a complaint has been made, and the complainant does not receive a copy of their own complaint, and other group members are not notified that a complaint has been raised. Perhaps surprisingly no record of the complaint appears in the group’s Activity Log.   

At this point the matter is firmly the responsibility of the Owner and Moderators to take such action as is necessary. It is not the purpose of this wiki to tell Owners and Moderators how to do their job, but it is strongly advised that if the complaint is deemed valid that the originator and complainant should be separately advised of that fact, with suitable words of advice given to the originator.

For a complaint to Groups.io Support about a perceived ToS violation, the message is sent only to Groups.io. As above there is no notification to the originator, the complainant, the wider membership, nor the Owner & Moderators. Again no record of the complaint being made will appear in the group’s Activity Log. The message again remains on the group’s web UI. It is not possible for this wiki to comment upon what action Groups.io might take if it is agreed that a ToS violation occurred, or indeed if it was decided that no violation had taken place.

Every effort has been taken to verify that the information above is correct (24th January 2019) but it has been written on an "E & OE" basis.