What is FastmailUA?
FastmailUA is Fastmail's content fetcher and image proxy service that retrieves external images and content for email security. It protects users from tracking pixels and malicious content by proxying external resources through Fastmail's secure servers. You can set up Agent Analytics to see when FastmailUA visits your website.
Category
| Example User Agent | Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/118.0.5993.117 Safari/537.36 FastmailUA/1.0 |
| Operated By | Fastmail |
| Source | Official Website |
| Triggered By | Shared link |
| Used for AI Model Training | Not expected |
| Affects AI Chat & Search Visibility | Not directly |
| Expected To Follow Robots.txt | No |
Why Is FastmailUA Visiting My Website?
Someone shared a link to your page. FastmailUA fetched it to build a preview card, and each new share may trigger another request. A spike often means your content is circulating more widely.
Should I Block FastmailUA?
Usually not. Blocking FastmailUA may leave shared links without a title or image, making them less inviting to click. If it begins fetching at unexpected volume, try rate limiting before blocking it outright. For context, 7% of the top websites we track currently have robots.txt rules for FastmailUA.
Insights for FastmailUA
As of October 30, 2026, this data reflects agent visits measured across thousands of websites using Agent Analytics, combined with daily scans of the top 1000 websites and their robots.txt files.
Robots.txt Compliance
Country of Origin
Robots.txt Blocked Percentage
Frequently Asked Questions
What Traffic Patterns Should I Expect From FastmailUA?
FastmailUA usually makes a single request within seconds of a URL being shared, without crawling further. Traffic rises and falls with sharing activity, so a widely circulated link can produce a sharp burst of fetches.
Does FastmailUA Follow Robots.txt Rules?
No. FastmailUA is not expected to follow robots.txt rules, so a disallow rule only communicates your preference. Enforce the block with firewall or server rules, then use Agent Analytics to verify that its requests stop.
Is FastmailUA Used for AI Model Training?
Not ordinarily. FastmailUA is not categorized as an AI training scraper or data provider, so AI model training is not its expected purpose.
Does Blocking FastmailUA Affect AI Search or Citations?
Not directly. FastmailUA's expected purpose is not to supply an AI search index or retrieve pages for AI-generated answers.
Does FastmailUA Access Private Content?
No. FastmailUA has no credentials and should access only the public URL and assets needed for a preview. It does not continue through the rest of your site.
How Can I Verify a Request From FastmailUA?
Agent Analytics tracks FastmailUA visits in real time. You can also check your server logs for requests whose user-agent string contains "FastmailUA". Look for a page and its preview assets being requested without follow-up navigation. Because FastmailUA does not publish a verification method, any client can claim its identity and a log match is only a clue.
How Is FastmailUA Different From Other Fastmail Agents?
Fastmail operates separate agents for different purposes, so each agent should be evaluated and controlled independently.
- Fastmail Bot: Fastmail Bot is a fetcher operated by Fastmail.