If someone has sent an email to you but it never has arrived, there are several things you can do to try and check.
Check your Junk Email folder
In the Outlook folder list, choose the Junk Email folder and look for the missing email.
If there are messages that shouldn't have been marked as junk, right-click each email and then choose Mark as not junk. The message will automatically be moved to your inbox.
Check your mailbox space
If your mailbox is full, you won't be able to receive new messages and send messages out. You can check the size of your mailbox by opening Outlook and clicking File. In the Mailbox Settings section, an indication of your mailbox size should appear.
If the space is full, please submit a support request for Real World Technology Solutions support team to help with options such as adding additional subscription licenses that can expand your mailbox storage or enable an online archive mailbox to your account to store additional data.
Note: It is NOT recommended that you create a new local PST file to store mail data. A PST file to store mail takes messages out of your mailbox and the Microsoft 365 service. If a storage problem occurs with your device or it is lost, the email it stores may be lost.
Check with your company's policy regarding the storage of emails to ensure against record loss.
Check your Inbox filter and sort settings
If your inbox is filtering based on categories or if your sort order is different than usual, you might not see the messages you expect to see. Filtering and sorting are accessible at the top of your message list.
For filtering, select Filter, then select what type of messages you want to see.
For sorting, select Filter > Sort by then what you want to sort by.
To look for recent messages, sort by Date. To look for messages from a specific person, sort by From. You can reverse the sort order by choosing the option again.
Check the Other tab
Focused Inbox separates your inbox into two tabs, Focused and Other, to help you focus on the messages that matter most to you.
If Focused Inbox is enabled for you, some messages sent to you might be in the Other tab. You can right-click any messages you want to appear in Focused and select Move to Focused inbox or Always move to Focused inbox. Focused Inbox will learn which messages should go always go to the Focused tab
Check your Blocked senders and Safe senders list
In Outlook, right-click any email message, choose Junk, then Junk E-Mail Options.
Click the Blocked Senders tab and check for any email address that may stop emails from a recipient being received. If found, highlight the entry and then click Remove.
You can also add an email address as a Safe Sender to try and have Outlook receive messages from a specific sender.
Click Safe Senders, then Add... In the box, enter the email address of the sender and then click Add.
Additional email protection settings that apply to your Microsoft 365 tenancy may still override the settings you make here, especially if email content contains a known virus or malicious content.
Check your email rules
Sometimes a rule may perform an action on an email message as it is being delivered to your maibox. Actions such as moving emails to different folders in your mailbox or forwarding them to recipients might have been applied and forgotten about.
To check rules, in Outlook, click File. In the Rules and Alerts section, click Manage Rules and Alerts.
Review any rule that has been created to determine if they may affect messages being delivered to you. You can disable a rule temporarily by clearing the tick next to a rule. If a disabled rule seems to correct the issue and emails are received correctly, you can delete the rule or modify it to prevent from affecting future messages.
Check if your account is blocked
In a web browser, visit https://outlook.office.com and sign-in with your Microsoft 365 user account.
If you can sign-in and view your email messages in the web version of Outlook, your account is not locked. If you get an error when signing in, please submit a support request for Real World Technology Solutions support team to help with unlocking your account.
Check email forwarding
In a web browser, visit https://outlook.office.com/mail/options/mail/forwarding and sign-in with your Microsoft 365 user account.
If forwarding is enabled and an email address or user account is present, emails may be forwarded to the other account as they are received to your maibox.
If Keep a copy of forwarded emails is not checked while forwarding is set to a user, messages will not be retained in your mailbox after they have been forwarded.
Contact the sender
If you've tried the solutions above and still aren't receiving messages from a sender, contact the sender.
Let them know that their email isn't being delivered to your mailbox and if they are experiencing any issues with their mail services. Ask to have them compose and send a new message to you to test, without specific wording or attachments that email protection system may interpret as spam or malicious preventing sending or delviery.
If you continue to experience issues with Outlook not responding, processing, or freezing - please submit a support request for Real World Technology Solutions support team to investigate further. Be sure to include as much detail as possible about Outlook's issue including if consistent, the times the issues tend to occur, the size of your mailbox and information on your internet connection and usage.
If unsure about the steps to perform or would like Real World Technology Solutions support team members to assist and perform - please submit a support request for remote support session.