If you look at your message queue and note some emails haven't been sent, then please follow these steps before submitting a support ticket.

Step 1) In Admin > System > Message Queue, take a look at which account(s) the unsent emails are being sent from. This will tell you which email account to check: 

Step 2) From here you can go to Admin > Configuration > Email Accounts and find the Account in question and "Edit". 

Step 3) Check the credentials, make sure all the fields are filled in correctly (for more information please see this article) and use the test email tool at the bottom of the page. 

- if the email sends, then please raise a ticket with these steps and we will investigate further why you have unsent emails. 

- if the email doesn't send and you get an error, please go to https://smtper.net and test your email account credentials. Please share that information / error with your internal IT Team and ask them to check the account setup or the host. 

 
Please note: if you are using one of the temporary email accounts provided by Infigo and emails aren't sending, it could be because the "email address" and "user" fields in the Email Account Setup don't match. To understand more about this, please see this help article https://infigosoftware.zendesk.com/hc/en-us/articles/16731838285074-Reverting-your-infigomail-net-email-account