Undo Send allows you to have a few seconds after you hit "Send'", to change your mind. It will put a little "Undo" option at the top of your inbox when it notifies you that your message has been sent. It doesn't actually recall your message, it just adds a delay between the moment you hit "Send" and the moment the email actually gets sent. During this delay window is when you have the option to click "Undo" and prevent the message from getting sent.
To turn on the undo send feature, click on the gear in the upper right corner of your inbox and select "Settings" from the menu. Scroll down until you see the "Undo Send" section. You can click the box to enable the feature and then use the drop down to choose how long after you hit "Send" you'd like to have the option to undo. You can choose 5, 10, 20, or 30 seconds. Be sure to scroll to the bottom of the page and click "Save Changes" before you return to your inbox.
Conversation view is a love/hate type of feature. Either you love it, or you hate it. I tend to like it, but I know many who have rejoiced when I showed them how to turn it off. Conversation view is what takes an email and groups it in with all the replies and/or forwards that stem from it. Without conversation view, each email you send, and each reply you receive, becomes its own email line in the inbox.
To turn conversation view on or off, click on the gear icon in the upper right corner of your inbox and select "Settings" from the menu. Scroll down until you see the "Conversation View" section. You can click the bubble to turn conversation view on or off. Be sure to scroll to the bottom of the page and click "Save Changes" before you return to your inbox.
Send and Archive is handy feature if you like to keep your inbox clean. Archiving your mail takes a conversation out of your inbox. Unless it has another label of some kind, it will only be found in the "All Mail" section. (You can find "All Mail" in the left-side navigation panel.) These emails will not clutter up your inbox, but will show up if you do a search. Since the search feature in Gmail is all kinds of powerful, my advice is to archive emails to your heart's content! Send and Archive puts another button right next to the "Send" button when you are composing a reply or a forward. You can choose to send the email and leave it in the inbox list by clicking "Send" as normal. If you click "Send and Archive" it will send the email and then archive the conversation, clearing it from your inbox list.
To show the Send and Archive button, click on the gear icon in the upper right corner of your inbox and select "Settings" from the menu. Scroll down until you see the "Send and Archive" section. You can click the bubble to show or hide the "Send and Archive" button. Be sure to scroll to the bottom of the page and click "Save Changes" before you return to your inbox.
You've probably noticed the little star to the left of each email. You can click this star to mark the email. You can easily see all the emails you have marked by clicking on the "Starred" section in the left-side navigation panel. There are a variety of star icons you can choose from. If you have more than one selected, you can click the star more than once to toggle through your options. Once you find the one you'd like, stop clicking and it will stay. To clear the 'starred' status from the email, just click the icon again and it will clear.
To choose which star icons you'd like to have in use, click on the gear icon in the upper right corner of your inbox and select "Settings" from the menu. Scroll down until you see the "Stars" section. You can drag the star icons back and forth from "in use" to "not in use" to choose your set of icons. Be sure to scroll to the bottom of the page and click "Save Changes" before you return to your inbox.
Setting up a signature can be very helpful, especially if you like your email recipients to have your contact information. Most people include their name, job title, and/or phone number in their signatures. Once you set it up, it will automatically show up when you send an email.
To set up your signature, click on the gear icon in the upper right corner of your inbox and select "Settings" from the menu. Scroll down until you see the "Signature" section. You'll want to click the bubble to enable the signature function and then design your signature. You can include text and images. I also like to check the little box at the bottom that will insert the signature before any quoted text in a reply. Once you are finished, be sure to scroll down to the bottom and click on "Save Changes" before returning to your inbox. You signature will now appear each time you click "Compose", "Reply", or "Forward".
The "Vacation Responder" feature is handy for when you will be out of the office or unable to read/reply to emails for an extended time. You can set this up to automatically reply to anyone who sends you an email during a certain period of time. You can set it to reply only to those in your contacts, or only to those in your organization. If you don't choose either of those options, it will send it to anyone who sends you an email.
To set up the vacation responder, click on the gear icon in the upper right corner of your inbox and select "Settings" from the menu. Scroll all the way to the bottom until you see the "Vacation Responder" section. Click the bubble to turn on the responder. Select your date range and type in whatever you'd like the subject of the automatic email to be. Type the message you'd like to send out in the white box. If you'd like to limit the responses to those individuals in your Contacts or in your organization, you can do so by clicking one or both of the check boxes at the very bottom. Be sure to click "Save Changes" at the bottom before you return to your inbox. The vacation responder will send out emails accordingly during the specified date range.