To validate your email, we recommend two complementing methods. You could also choose only one of the two methods. With the first method, you could do a prior sending by using a test group to validate your content (personalization for different audiences, visual rendering and targeting criteria). This way, you can correct errors before the final sending. Make sure you target the right contacts for the test by using a criterion that limits the targeting to internal contacts (administrators, managers).
With the second method, after the testing, you will proceed to a final sending to your contacts. When you choose your recipients, you could then include a seed list group to validate the reception of this final sending. Thus, you could react faster if your messages are not delivered or if an error is remaining (e.g. wrong price or date). Contacts on the seed list are generally internal users (e.g. store managers) who want to validate the content or simply receive it. Eligibility rules do not apply for seed list contacts, which means they will receive the communication even if they have not subscribed, are not eligible to a communication type or the profile of the contact is deactivated. So, make sure to have their permission.
Validate the Content With a Test Group
1. Create a test group
Start by creating a group by checking Test group:
You could also check Seed list group, so you can also use this group for the seed list validation.
Next, add one or several criteria to limit the targeting to contacts from your company. Then, add other criteria that correspond to these contacts (and to the content personalization included in your communications). Make sure not to target external clients for whom you do not have permission.
2. Select the test group
When your message is ready, go to Test. In the left menu, select the test group in the list: 
3. Send the message.
Click Send to proceed with the test sending. Afterwards, validate with the contacts of the group that everything works as it should.
Validate the Reception With a Seed List
1. Add contacts to seed list
Start by manually adding contacts that you want to use for the seed list group. Go to the profile of each contact and click Add to seed list:
2. Create a seed list group
When creating a group, select Seed list group. A contact added to the seed list (through the profile) will be automatically included in this group, except if you add criteria that do not target this contact.
You could add up to 100 seed list contacts to the sending. In the Send interface, check Include seed list group and choose the group in the list:
Note: a contact included in one of the selected groups as well as the seed list group will only receive the message once, as a seed list contact.4. Send the message
Finally, when your message is ready, click Prepare mailing and proceed with the final sending. This is not a test: This message will be sent to included contacts!
Results
You could see contacts of a test or seed list group using the Search feature by adding the group as a criterion.
In the Edit interface, you can see the list of targeted contacts by the selected group and visualize the personalized version of the message for a specific contact. 
The T symbol represents a test group, and the person symbol, a seed list group.