The size of the largest allowable email depends on your membership level. For details see the pricing table . These are the sizes of attachments you are allowed. Due to the way that emails are encoded, an email with 10M of attachments could use 14-15M of quota - see Bandwidth Usage .

If you reach 50% of a particular hourly limit (number of emails sent, hourly transfer quota) you'll be sent a warning email (both to your FastMail.FM account, and your existing/backup email address). If you reach 100% of an hourly quota, your account will automatically be locked for one hour. This is automatic, and cannot be disabled for individual accounts. If you reach a limit, you should wait for an hour for your account to be automatically re-enabled.

When you reach 75% of your monthly bandwidth quota, you'll be sent a warning email (both to your FastMail.FM account and your existing/backup email address). You should probably upgrade your account, or purchase additional bandwidth at this point. If you reach 100% of your monthly bandwidth quota (including excess bandwidth you've bought), you'll have sending/receiving of email disabled for your account. If you reach 150% of your monthly quota, your account will be locked until the end of the month.

You can use FastMail.FM for SafeLists, but you should be careful. SafeLists often generate A LOT of email traffic, which can cause your account to reach our hourly quota limits .

If you plan to use SafeLists, you should sign up for a Full or Enhanced account, and also make sure that you don't sign up to so many lists that you receive over 1000/2000 emails each hour (as appropriate for your service level).