What is the optimal length for an email address in a database?

Question

Here is an extracted portion of my query, reflecting the EMAIL_ADDRESS column data type and property:

EMAIL_ADDRESS CHARACTER VARYING(20) NOT NULL, 

However, John Saunders uses VARYING(256).

This suggests me that I have not necessarily understood the VARYING correctly.

I understand it such that the length of an email address is 20 characters in my case, while 256 for Jodn.

Context in John's code

CREATE TABLE so."User"
  (
    USER_ID SERIAL NOT NULL,
    USER_NAME CHARACTER VARYING(50) NOT NULL,
    EMAIL_ADDRESS CHARACTER VARYING(256) NOT NULL, // Here
    HASHED_PASSWORD so.HashedPassword NOT NULL,
    OPEN_ID CHARACTER VARYING(512),                                                         
    A_MODERATOR BOOLEAN,
    LOGGED_IN BOOLEAN,
    HAS_BEEN_SENT_A_MODERATOR_MESSAGE BOOLEAN,
    CONSTRAINT User_PK PRIMARY KEY(USER_ID)
  );

I have never seen email addresses longer than 20 characters, used by ordinary people.

What is the optimal length for an email address in a database?

Answer 1

The maximum length of an email address is 254 characters.

Every email address is composed of two parts. The local part that comes before the '@' sign, and the domain part that follows it. In "[email protected]", the local part is "user", and the domain part is "example.com".

The local part must not exceed 64 characters and the domain part cannot be longer than 255 characters.

The combined length of the local + @ + domain parts of an email address must not exceed 254 characters. As described in RFC3696 Errata ID 1690.

I got the original part of this information from here

Answer 2

from Ask Metafilter:

My data comes from a database of 323 addresses. The distribution has some upper-end outliers (positively-skewed). It is normally distributed without the outliers (I tested it.)

Min: 12 1st quartile: 19 Mean (w/ outliers): 23.04 Mean w/o outliers): 22.79 3rd quartile: 26 Max (w/ outliers): 47 Max (w/o outliers): 35

Median: 23 Mode: 24 Std. Dev (w/ outliers): 5.20 Std. Dev (w/o outliers): 4.70

Ranges based on data including outliers 68.2% of data 17.8 - 28.2 95.4% of data 12.6 - 33.4 99.7% of data 7.4 - 38.6

Ranges based on data outliers excluded 68.2% of data 18.1 - 27.5 95.4% of data 13.4 - 32.2 99.7% of data 8.7 - 36.9

If you sign up for http://www.abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghijk.com/ then your email address would surely be an outlier :)

Here's What is the maximum safe length of an email address to allow in a website form? on Raycon with a slightly different mean (N=50,496, mean=23):

Answer 3

Just use varchar(50). Longer emails are crap, every time.

Just look how long 50 chars is:

peoplewithanemail@ddressthislongjustuseashorterone

If you allow 255 character emails:

• Displaying them can mess up your UI (at best they will be cut off, at worst they push your containers and margins around) and
• Malicious users can do things with them you can't anticipate (like those cases where hackers used a free online API to store a bunch of data)

(Statistics show that no-one actually enters more than about 50 chars for a legit email address, see e.g.: pageman's answer https://stackoverflow.com/a/1199245/87861)

Answer 4

My work email address is more than 20 characters!

Read the appropriate RFC specification:

"The local-part of an e-mail address may be up to 64 characters long and the domain name may have a maximum of 255 characters"