Starting in April 2015, 1&1 began offering unlimited e-mail accounts and storage with the Unlimited Plus and Unlimted Pro packages. All other packages and packages purchased before April 2015 come with 1&1 Mail Basic accounts are limited to 2GB.
* The limits above assume that you are sending from a 1&1 mail account to another 1&1 mail account of the same type. Some e-mail providers will reject an e-mail if the file size exceeds their maximum file size, which could potentially be lower than the limit imposed by 1&1. If so, you will receive a bounceback message from that e-mail provider informing you that the mail was not delivered because the attachment is too large.