E-mail validation is too strict about the characters it allows in the local part of the address (the part before @ sign), and disallows characters such as : and &.

According to RFC2822:

addr-spec = local-part "@" domain
...
The local-part portion is a domain dependent string. In addresses,
it is simply interpreted on the particular host as a name of a
particular mailbox.

IOW, only the host can decide what is valid on the left side of the e-mail address.