Question

I recognize that an email address can basically be indefinitely long so any size I impose on my varchar email address field is going to be arbitrary. However, I was wondering what the “standard” is? How long do you guys make it? (same question for Name field…)

update: Apparently the max length for an email address is 320 (<=64 name part, <= 255 domain). Do you use this?

Answer 1

The theoretical limit is really long but do you really need worry about these long Email addresses? If someone can’t login with a 100-char Email, do you really care? We actually prefer they can’t.

Some statistical data may shed some light on the issue. We analyzed a database with over 10 million Email addresses. These addresses are not confirmed so there are invalid ones. Here are some interesting facts,

1. The longest valid one is 89.
2. There are hundreds longer ones up to the limit of our column (255) but they are apparently fake by visual inspection.
3. The peak of the length distribution is at 19.
4. There isn’t long tail. Everything falls off sharply after 38.

We cleaned up the DB by throwing away anything longer than 40. The good news is that no one has complained but the bad news is not many records got cleaned out.