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 NU         


        

Answer 1

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"

Answer 2

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 "user@example.com", 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 3

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 4

Variable character types in databases don't occupy unneeded space. Thus, there is no reason to constrain such fields as much as possible. Depending on the name of a person, the naming scheme used by their organization and their domain name, an address can easily exceed 20 characters.

There is no limit as to the length of local-part and domain-name in RFC-2822. RFC-2181 limits the domain name to 255 octets/characters though.

Again, since a varchar only uses the space actually used by the string you store, there is no reason to have a small limit for email address length. Just go with 512 and stop worrying. Everything else is premature optimization

Answer 5

As others have said, way bigger than 20. 256 + 64 sounds good to me, and is RFC compliant.

The only reason to not have such a large value for your database is if you are worrying about performance or space, and if you are doing that then I'm 99.99999999999999% sure that is premature optimization.

Go big.

Answer 6

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)