Being the CEO of my e-mail marketing company VerticalResponse, I'm always on the lookout for low-cost or free tools that can make my life and the lives of our customers better in small and big ways.

In our busy office, we use the heck out of Google, from Drive and the Calendar to Analytics. We've tried heaps of others and we always come back to these tried-and-true tools. They're easy to use, reliable and robust enough to handle the needs of a 110-person (and growing!) company. So this week, I'm going to share three of my favorite Gmail plug-ins. And the best part is, they're all free. 

BoomerangBoomerang

We're all looking for better ways to manage our e-mail inbox and several apps have popped up this year, including the much hyped-about Mailbox app for the iPhone and Gmail. But I want to call out a particular e-mail app called Boomerang, which also works with Outlook. What I like about Boomerang is its ability to do three key things:

1. Schedule an e-mail to be sent later. You can write an e-mail now and schedule it to be sent automatically at the perfect time. Just write the message as you normally would, then click the "Send Later" button. Use a handy calendar picker to select your date and time.

2. Pause messages until you are ready for them. Use Boomerang to take messages out of your inbox until you actually need them. Just click the Boomerang button when you have an e-mail open, and choose when you need it again

3. Set follow up reminders. There are times you need to make sure you follow up within a specific time frame after sending a message. You can select to only be reminded if nobody replies, or regardless. This way messages won't slip through the crack and you won't forget to follow up with folks.

Cost: Starts at free for basic version, up to $14.99/month for professional version.

Attachements.meAttachments.me

Attachments.me hooks up your Gmail with cloud storage services Dropbox, Box, and Google Drive. (Personally, I'm a fan of Google Drive and Dropbox.) So instead of uploading an attachment, you can simply insert a file from the cloud right into your e-mail. Your sent files will also automatically be backed up on your cloud account. You also get cool bennies like having your files password-protected or setting the links to expire on a certain date.

Fast and flawless--just how I like it.

Cost: $0 to $9/month.

StreakStreak CRM

The folks at Streak let you have a simple customer relationship management (CRM) tool right inside your Gmail. According to their website, "Streak was born out of the frustration of constantly having to switch between our inbox (where we do our work) and separate systems. Our goal is to take the work out of managing the processes you do everyday." And as the name implies, they want to help you do it fast.

I can see sales folks loving Streak because you can track all of your deals right from your inbox. And you can see all the e-mails that have gone back and forth and get all the context you need in one place. Like Boomerang, Streak also allows you to write an e-mail now and schedule it to send later. And Streak works across all your Gmail accounts and can be used simultaneously, so you could use it with your work and personal accounts if need be.

Cost: free (but the website says they will soon offer paid premium features, too)

Do you have some favorite Google (or other) plug-in tools to add to my list to try? I'd love to hear 'em in the comments.

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