Canned responses are the email templates that we can use multiple times. We will use this idea to create multiple signatures as different canned responses that can be inserted anytime with ease.
Multiple Canned Responses for Different Signatures:
First, we need to enable Canned Response feature from Labs in Google Settings. Go to Gmail Settings > Labs > Enable Canned Responses > Save. Now, compose a new mail enter the signature you want to have. From the bottom right options menu and chose Canned Responses. Click on ‘new canned response’ to save it. Give it a name so you can access it later. We can discard this new email but your signature will be saved as a canned response on the name that you gave. Repeat these steps – Create signature > Save as new canned response > discard the email. That’s all! You have created multiple Gmail signatures. Now whenever you want to use a different signature, just insert the saved canned response before drafting your mail. Bonus: This technique also solves the three dot problem of Gmail hiding signatures from mail content. Canned responses are not the most optimum way for handling different signatures. There is still lot of manual work involved and you cannot have rule based signatures i.e. one signature for replying, another one for forwarding and another when composing. But this is the most practical way without any extensions or third party softwares. You can WiseStamp or AutoHotkey for automation and switching signatures in the fly. For AutoHotkey script, follow instructions here. WiseStamp is easy to use but are you ready to give access to your mailbox?