Add your html signature to Thunderbird
Open thunderbird, go to the account you want to add the signature to, then just choose "View settings for this account"
Below is what you should see now, you then just have to check the "Attach the signature from a file instead (text, Html, or image):"
, then just choose your html signature file.
That's it, you are all set, now you just have to write a new message, and you should see you signature appearing sat the end of your message! You will see a red dashed border around your signature, but don't worry, none of your clients will see it on your sent emails.
Add your html signature to Microsoft Outlook
For outlook, the process will be similar to the thunderbird one, at least as simple. Just go to tools, and choose "Options"
Choose the signature tab, there, first click the "New" to add a new signature, check the "Add signatures to all outgoing messages"
, choose the html signature, and click "Apply"
Now just create a new email, and you can see your signature at the end of the message, that's it
Add your html signature to Apple Mail
Now the trickiest one for all of you Apple lovers, mail is just my preferred email client, but i have to admit that it's a bit complicated to add your html signature, so will try to make it as easy as it can be.
First, open mail, and go to the preferences (command+,). Go to the signatures tab, add a new signature by clicking the "+" and rename it with the name you want. Add some random text to that newly created signature.
Ok, now you just created a new signature, open the finder and go to your User/YourUserName/Library/Mail/signatures/ . You can now see a file with .webarchive extension. Don't take too much attention to that now, but remember that we will save our html signature to that specific place just after.
Next, open your signature.html with safari, and save it (command+s), just choose the same folder you have your mail signature (User/YourUserName/Library/Mail/signatures/) and just click on the existing signature so the file you are saving will have the exact same name. Verify you can see the webarchive extension at the end and click save.
That's it, just quit mail, and restart it. Try to type a new message and you should have your beautiful html signature at the end.
Hope this will be helpful, thanks for reading.

