The AutoComplete list is updated automatically after sending an email (see more about AutoComplete feature). To make it easier to work in Outlook, you can add useful email addresses to your AutoComplete list without sending emails.

By default, Outlook uses the AutoComplete list to suggest email addresses. If the AutoComplete feature is not disabled in Outlook (see how to turn it off), the AutoComplete list is updated automatically after sending an email. From time to time, people make mistakes when entering addresses or receive incorrect addresses for use.

The AutoComplete feature generates an AutoComplete list, also known as the nickname cache. This list is generated automatically after sending email messages from Outlook:

Users of Microsoft email services are well acquainted with the OST format, which is used to store data in encrypted form. Converting OST files allows you to get rid of format restrictions, after which mailings will become available to the user for offline work in Outlook.

Recovery Toolbox for Outlook represents a powerful data recovery software for repairing email records in OST or PST format. Typically, the loss of Outlook content can become a real problem regardless of the computer where it took place: either in a work environment or at home PC.

Corruption of Outlook data files (.pst) renders the mailbox data inaccessible. It is practically impossible to get back the complete mailbox data from corrupt PST files with the help of built-in utilities, as it often happens to large size PST files. Outlook PST repair tool from Stellar Repair for Outlook effectively fixes large inoperable or severely corrupt Outlook data files.

If Outlook does not open your data file, or you can not find some items in your inbox, contacts or calendar, then your PST is apparently corrupted. At this moment, thought about backup comes to your mind, but it is too late to muse about a backup. You need to backup your Outlook data in advance. Otherwise, you will need a repair tool.

Time to time, when you send an email, you need to keep the text of the previous messages intact. E.g., if you use AutoCorrect in Outlook to check errors before sending any message, but you need to keep original text without any changes.

If your data files in Outlook won't open, or items appear to be missing in your inbox, then your PST file is probably corrupted. However, there is a way to recover your emails, contacts, calendars, notes, etc.

It is polite to reply to every received message, even if you don't have a time to process the message. To create a rule to reply for messages, see How to auto respond for some messages.
Sometimes you can't create a rule for some incoming messages because of unusual subjects, etc. So, you need to answer very quickly and work with messages later.