What special characters are allowed in email address syntax according to RFC 5322 and how do different email providers handle them?

Marketer from Email Geeks explains that as per RFC 5322, section 3.2.3, the provided email address syntax is valid. The definition of “atext” lists the allowed characters, as clarified in section 3.4.1.

Email marketer from ZeroBounce states that email address validation helps ensure that you only send emails to real users and avoids sending emails to invalid addresses which can harm your sender reputation.

Email marketer from Clearout mentions the local part can have a maximum of 64 characters, and domains have a limit of 255 characters. The entire email address has a length limit of 320 characters.

Email marketer from Email Hippo highlights the significance of email address validation in maintaining a clean email list and improving deliverability, especially concerning the acceptance of special characters.

Email marketer from StackOverflow shares that many validation libraries and regular expressions used for email validation are overly restrictive and do not accurately reflect RFC 5322, leading to the rejection of valid email addresses. They recommend careful testing and consideration of the specific requirements.

Email marketer from Experian warns about the negative effects of bad email data including incorrect or invalid formats and the potential impact on marketing campaigns and sender reputation.

Email marketer from Reddit states that Yahoo often rejects email addresses with unusual special characters in the local part, even if they are technically valid according to RFC 5322.

Marketer from Email Geeks points out that RFC 5322 permits some special characters but forbids others, linking to the relevant section.

Email marketer from SendGrid explains that many email providers have stricter rules than RFC 5322. They often disallow special characters like `!` or `#` at the beginning or end of the local part, or consecutive periods.

Email marketer from Mailjet explains that Gmail ignores periods in the local part of an address (e.g., `john.doe@gmail.com` is treated the same as `johndoe@gmail.com`).

Email marketer from Kickbox warns that using email addresses with invalid characters often lead to hard bounces, damaging sender reputation.

Email marketer from Validity notes that while RFC 5322 provides a baseline, each email provider can implement its own additional restrictions on allowed characters in email addresses.

Expert from Word to the Wise, Laura Belgray, responds to a user question about allowing international characters. It states that you should avoid these characters because they will cause deliverability and technical issues.

Expert from Email Geeks clarifies that valid syntax doesn't guarantee deliverability and maintaining a list of rules enforced by each MX provider is an attempt to reverse engineer something that changes, the usefulness of which depends on why one wants to know.

Expert from Spam Resource discusses that while RFC specifications define the allowed characters in email addresses, deliverability depends heavily on the policies and filtering rules of individual mailbox providers. Using less common special characters might trigger spam filters, even if technically valid.

Expert from Email Geeks notes that the local part isn’t a string, it’s one or more atoms separated by periods, or a double-quoted string. That means you need to be aware of the rules around atoms (leading, trailing or doubled periods, for example) if you’re writing code around them.

Expert from Email Geeks explains that any character is allowed inside a double-quoted string. The "do not appear in atext" list are not allowed outside a double-quoted string.

Expert from Email Geeks suggests that blanket rules should align with the RFC, and no more.

Expert from Email Geeks explains there are two levels of "valid" - valid address syntax and valid syntax for specific providers like Gmail. Just because it's valid syntax doesn't mean Google allows it.

Documentation from ietf.org clarifies that RFC 5322 allows any character within a quoted string in the local part of an email address. However, the implementation of quoted strings may vary among different email providers.

Documentation from Wikipedia outlines that while RFC 5322 defines the standard for email address syntax, practical implementation often differs. Some providers may not support all characters allowed by the RFC, particularly special characters in the local part.

Documentation from ietf.org specifies in RFC 5322, section 3.2.3, the characters allowed in 'atext' which are used to form email addresses. These include alphanumeric characters and the following special characters: `!`, `#`, `$`, `%`, `&`, `'`, `*`, `+`, `-`, `/`, `=`, `?`, `^`, `_`, `` ` ``, `{`, `|`, `}`, `~`.