Aliases:
- Fastmail domains: 2 or more characters in length. The alias must start with a letter, must not end in a period character, and can contain a-z, 0-9, period, or underscore.
- Personal domains: 1 or more characters in length. The alias must not start or end with a period. The other characters can be a-z, 0-9, period, or underscore.
- The limit for the number of aliases is shown in the account/limits link I gave. It is 600, plus 15 for every user in the account.
Identities (sending From addresses):
Fetch accounts (POP3 fetch):
The limits on attachment size and numbers of messages sent are also described on this help page. The limit on attachment size is 70 MB after encoding:
https://www.fastmail.com/help/account/limits.html
Bill