Regular Expressions: email addresses

Write the regular expression that represents all valid mail addresses with domain name mail.com. Assume that valid email addresses contain only small letters [a-z] and digits [0-9], and they always start with a small letter. Provide two solutions:

**Note: The following mailing addresses are not real**

1. Assume that the maximum email address for the domain asu.edu has length 5. E.g., syn@mail.com and synth@mail.com are valid, but synthi@mail.com is not.

2. Assume that there is no maximum email address length.