GMail does not limit you to using just one e-mail address. You can integrate your web client with other accounts. What's more, not only can you download the messages from other inboxes, but also send your messages from GMail level from other e-mail addresses.
Importing your e-mail settings in GMail is extremely easy. First of all you have to go to Setting by clicking on the icon of a gear-wheel in the upper right corner of the interface. Next you have to go to Accounts and importing label. Here you will be able to add new addresses.
Click on Imports e-mails and contacts, and then in a new window choose the e-mail address you would like to import. Then you have to provide GMail with the password to the imported account. Afterwards you can choose what do you want to install - contacts, e-mails, etc. You can also create a separate label for that account.
To send e-mail from other addresses go for Send e-mails as -> Add a new e-mail address. Here you can add another e-mail address you own. Provide the wizard with the name that will be displayed next to it, along with that e-mail address. You can choose easier configuration (Send via GMail) or more difficult (via SMTP). In the case of the first one you only have to verify a special code that will be sent to the inbox that is supposed to be added to your GMail account.
After the configuration process you can compose a ew e-mail message. In From: field you can now choose the newly added e-mail address. If you want to set it as a default one, go to Settings -> Accounts and importing again. Choose Send e-mails as: and set the address you want as the default. Voila!
