We apply fair use account limits across our service to prevent abuse or runaway activities from using up too many resources. In most cases, you will receive an automatic email notification if you have reached a limit on your account.
Details on our most common limits are below.
- Limits on storage space
- Limits on sending/receiving mail
- Bandwidth limits: Files and websites
- How attachments change message size
- Limits on logins
- Limits on rules
There are two main storage limits for every user: one is for mail, calendars and contacts, and the other is for file storage. The limit per user depends on your account plan, as detailed below.
You can see how much of your storage quota is being used by scrolling to the bottom of the sidebar in the Fastmail web interface.
You will receive an automatic email notification if you get close to your storage quota limit. You should either delete some of your existing data to make room (and make sure you empty your trash to recover the space if you are deleting mail), or add email storage quota or upgrade your account.
If you go over your mail storage quota, any further mail sent to your account will be temporarily bounced with a
4xx code. A
4xx bounce, also known as a soft bounce, means that the server will continue making attempts to deliver the message for some time. Therefore, if you get your account back under the storage limit quickly (either by upgrading your plan or deleting some existing data), no messages will be lost.
If your account remains over storage quota for a week, we will change to returning
5xx permanent error messages. This means all messages sent to your account at this point will bounce and be returned to the sender as undeliverable.
Attachments cannot be deleted from messages while you're over your mail storage quota.
These restrictions are lifted as soon as your account goes back under quota.
The following limits are per user, and are the same for all plans:
|Number of fetch accounts
|Number of contacts
|Number of calendar events
The following limits apply to the account as a whole, depending on the plan:
|Number of aliases
|600, plus 15 for every user in the account
|Number of domains
|100, plus 1 for every user in the account
Accounts are able to publish up to 100 static websites. All plans are able to set up websites, but only accounts on Standard and Professional plans are able to set up websites with custom domains.
You may send any kind of attachment, as long as the resulting email is under 70 MB in total size. Combined with email encoding, this usually means an attachment should be no larger than 50 MB. The same size limit of 70 MB applies to received email as well.
Attachments with double file extensions (e.g.
filename.doc.exe) as well as .pif, .scr, .cpl and .com files are not allowed, as these are commonly used when sending email viruses.
To protect our service against abuse, we limit the number and total size of emails that can be sent and received. These limits are very high and 99.9% of our users never get anywhere close to hitting them. If you find yourself regularly getting close to hitting the limit of sent/received messages for your account, you should upgrade your account. If you are already at the top plan, contact our support team to discuss your needs.
The following daily limits apply per user, depending on the plan:
|Number of messages received
|Total size of messages received
In addition to the daily limits, there is a per-minute limit of 100 messages and 100 MB. This limit is the same for all account levels and is to stop large email floods from overloading an account.
We also have limits for the number of received messages from a single sender. No mail being received from a single sender can exceed half of your per-day or per-minute allowance. This limit is in place to stop an automated system from accidentally flooding your account, which would then prevent other email addressed to you from being received.
Note: Fastmail is not a bulk email sending service. Our rate limits are designed to be generous for individual users, but not for bulk sending. Our Terms of Service prohibits sending duplicative email, and we will permanently close accounts found doing so.
The following daily limits apply per user, depending on the plan:
|All Trial users
|Number of messages sent
|Total size of messages sent
All trial accounts are limited to sending a maximum of 120 messages per day to prevent abuse. The sending limit is raised to the full account quota as soon as the account is paid for.
Please note that when you send an email to multiple recipients, this is considered one email per each recipient.
In addition to the overall daily limits, there are several other time-based sending limits. There is an hourly limit for each of these quotas which is half the daily limit, and a 10-minute limit which is half the hourly limit. There is also a smaller daily, hourly, and 10-minute limit on the number of distinct recipient addresses you can send to.
To protect our service against abuse, there are per-hour and per-day bandwidth limits for files and websites. They apply to how much is sent from your website (webpages and associated content), as well as what is uploaded and downloaded from your file storage. The bandwidth limits are dependent on your plan.
The following daily limits apply:
|All Trial accounts
|Number of files/webpages/images uploaded or downloaded
|Total size of files/webpages/images uploaded or downloaded
In addition to the daily limits, there is an hourly limit which is half the daily limit, and a 10-minute limit which is half the hourly limit.
Individual files cannot be larger than 250 MB.
When a limit is reached, further attempts to send/receive emails, upload/download files, or service webpage requests (depending on which limit was breached) will be blocked.
For emails, the block will cause incoming emails to receive a temporary
4xx type response, sometimes called a "soft bounce". This does not result in email being actually bounced, only delayed; the sending server should try again later.
The rate tracking counter is activated on the first event received of its type (email or file), and reset 1 minute/10 minutes/1 hour/24 hours after the first event received. We only update the rate tracking information after the request has completed.
Here's an example for a user uploading and downloading files with a 1000 MB hourly file transfer quota:
- 10 MB uploaded. Counter starts at 10:15. Counter = 10 MB.
- 20 MB uploaded. Counter = 30 MB.
- 500 MB downloaded. Counter = 530 MB.
- 500 MB uploaded. Counter = 1030M. You are allowed the download/upload event that sends you over the hourly limit, but none after that until the counter resets.
- 10 MB download attempt fails. Counter = 1030 MB, over the limit of 1000 MB.
- Counter resets.
- 200 MB downloaded. Counter starts at 11:30. Counter = 200 MB.
Email is an old standard that originally started as purely text data. Over time, as people wanted to send attachments, they updated the standard to include them, but also tried to keep it backward compatible so older email systems wouldn't "break" the messages.
To do this, any attachment added to an email is usually encoded into a form called "base64." In this system, each group of 3 binary bytes is encoded into 4 ASCII characters. This means a couple of things:
- All characters in emails are always ASCII so existing systems are not confused or broken.
- Any binary attachments are expanded by 1/
3 (33% bigger, so 30k becomes 40k, etc.).
Our IMAP server stores emails in their original form, so any emails with attachments will be about a third bigger than the actual size of the attachments when you download them. The sizes reported on the mailbox screen, and the totals reported on the resource usage screen are of the original email as it is stored in our server.
There is a per-user limit of 500 (successful) logins per 10 minutes across all services, including IMAP logins, POP logins, SMTP logins, etc. Most users will never get near this limit: it's there to protect against poorly implemented or designed software, or incorrect settings.
There is a per-user limit of 1000 rules.