I'm pretty sure that almost every one of you has more than one mailbox. Moreover, I do not mean the inevitable existence of a corporate mailbox for those who spend time in open-space. I mean only and exclusively personal mailboxes. And today I would like to tell you about Glen Allsopp's advice about switching to using one mailbox for everything.

Before moving to a single mailbox, you need to organize everything.
Indeed, it is stupid to carry all sorts of nonsense and waste time on it.

Unsubscribe from all newsletters you don't need, including notifications from social networks and forums.
Look for phrases that clearly can only be found in spam and delete them en masse.
Make sure that you have saved passwords and registration information anywhere.

After all your boxes are processed in this way, you can start merging.

Import all the necessary messages
When there is only what you need in the boxes, you can proceed with the merging procedure itself. How exactly this will happen depends on where you store your mail.
But you can find some tips here:

Switching from Hotmail to Gmail
Migration from Outlook to Gmail
Switching from Outlook to Thunderbird

If you need to do something else, Google it, almost certainly you are not the only person who wanted to do it, and the solution can already be described.

Configure redirection
After importing the old correspondence, you should configure everything so that all new emails are redirected to your main mailbox.
In the settings Gmail Settings; Forwarding you can add old addresses, enter a password and configure the rules for clearing the old mailbox. You can either delete an email after transferring it to a new one, or leave it in the old one too.
Redirection of mail in Outlook can be configured using rules, which is also not difficult. But this may require Outlook to be running.

Inform your friends and acquaintances and update the pages with your coordinates
Since you definitely don't want to keep programs open or hope that POP access won't be blocked for you, notify everyone about your new address. Don't forget social networks, blogs, forums – all the places where you have already lit up.

Choose your signature carefully
Some started several boxes just to separate work and personal space. If this is the case, it is probably worth continuing to maintain such a separation. However, not everyone needs this, but at the same time, when responding to a specific letter, pay attention to which signature you use: it should relate to the topic.

How to Consolidate Multiple Inboxes into One [ Glen Allsopp ]