How to add a signature in Fastmail, including an image

In Fastmail, each address or alias has its own signature. Go to Settings → My email addresses, open the Signatures tab, click the arrow next to an address in the Addresses without a signature section, type your signature, and click Save. Fastmail cannot take an uploaded file in the signature editor, so an image has to be a public web link.

How do I add a signature in Fastmail?

1. Click Settings → My email addresses.
2. Click the Signatures tab.
3. Find the address in the Addresses without a signature section and click the arrow beside it.
4. Type or paste your signature, then click Save.

Fastmail lists aliases without a signature in a separate group at the end of the page. If an address never gets a signature, look there first. To change a signature later, click the Edit button next to the address.

Why don't I see a formatting toolbar?

The toolbar appears only when your default message format allows rich text. With it, you can change fonts and colors and add links. If you don't see it, turn rich text on under Settings → Mail preferences.

How do I add an image to a signature?

Fastmail's help says the image must already be on the internet as a link. If you don't have an image host, upload the file to Fastmail Files first:

1. Open the Files screen, click Upload, then choose Upload Files.
2. Select the image and click Open.
3. Click the image, then click Share at the top of the screen.
4. Select Enable, then click Copy to Clipboard.

Then add it to the signature:

1. Go to Settings → My email addresses, click the Signatures tab, and click Edit next to the address.
2. Click the Image icon on the formatting toolbar.
3. Paste the image URL and click the blue Insert Image button.
4. Click Save.

Images hosted in Fastmail Files count toward your download limits. If the image will use a lot of bandwidth, Fastmail suggests an image hosting service instead.

How wide should the image be?

Keep it under 320 pixels. Fastmail does not shrink images, so the file you upload is the size every recipient sees. A wider image will likely force horizontal scrolling on a phone. Resize it before you upload. To check it on a phone, open Fastmail there and start a new email.

Why did the image stop showing?

Fastmail warns that if you don't own the image on the remote host, the server can remove or change it at any time, and your signature changes with it. Hosting the file yourself avoids that. Fastmail also reminds you to check that you have permission to use the picture.

On a multi-user account, an administrator has to upload the file for you and send you its URL.

What else should I check?

• The signature is missing from new mail. That address is probably in the Addresses without a signature group. Add a signature to it.
• The image is missing for recipients. Paste the link into a private browser window. If it doesn't load without signing in, recipients won't see it either.
• The formatting controls are missing. Turn on rich text in Mail preferences, as described above.

Where do replies and forwards get the signature?

Go to Settings → Mail preferences, scroll to When replying or When forwarding, and pick a Signature position: above the original message, below it, or not at all.

How Sendoff handles this

Images you upload in Sendoff are saved as public files and given a public URL, so you don't need a separate image host for a Sendoff signature. The signature checker flags relative image paths as errors, and flags http images and images with no width attribute as warnings. A live size meter tracks Gmail's 10,000-character limit. The checker does not test the 320-pixel width Fastmail recommends, so resize the image first.

Build the layout in the signature generator, then check the image rules above before you paste it into Fastmail.

Sources

• Fastmail Help, How to create a signature (signature, image, and reply options): https://www.fastmail.help/hc/en-us/articles/360058753754-How-to-create-a-signature
• Fastmail Help, Fastmail settings (Signatures tab and aliases without signatures): https://www.fastmail.help/hc/en-us/articles/6414132167311-Fastmail-settings