Comment by HackerNewt-doms

The mail service has several serious shortcomings: 1. Disposable addresses (with the prefix temp in the domain part of the email address) can be generated via the web interface. However, when I receive an email at such a disposable address and reply to it in the web interface, the From field does not show this disposable address used in the previous communication, but instead the standard email address of the mailbox account. This is extremely annoying, because this communication partner is only supposed to know the disposable address. 2. In addition to the limited number of disposable addresses provided by the mailbox service, it is also possible to generate countless email addresses in the form of +extensions to the standard local part of the email address itself. Here again, it is frustrating that these email+addresses cannot be selected as the sender in the mailbox web interface (in Thunderbird you can and in the iOS Mail app it only works after manually adding this extension email as an alias in the account settings of the iOS app).

Moreover, Mailbox.org restricts the creation of email extensions exclusively to the plus sign: with alice@mailbox.org you can generate alice+test@mailbox.org, which inbound will automatically be sorted into the inbox folder alice (case sensitive).

But Mailbox.org does not allow the creation of alice.test@mailbox.org, which would actually be accepted as a registration email address by significantly more online services, because many of them apply standard filter rules for valid email addresses that wrongly consider the plus sign invalid and therefore reject it.