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fix(gmail): RFC 2047 encode subject headers for non-ASCII characters #3526

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Merged
waleedlatif1 merged 4 commits into from
Mar 11, 2026
Merged

fix(gmail): RFC 2047 encode subject headers for non-ASCII characters #3526

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bc6c86b
fix(gmail): RFC 2047 encode subject headers for non-ASCII characters
waleedlatif1 Mar 11, 2026
f207f8e
Fix RFC 2047 encoded word length limit
cursoragent Mar 11, 2026
b05f0b3
fix(gmail): split RFC 2047 encoded words on character boundaries
waleedlatif1 Mar 11, 2026
12fd2eb
fix(gmail): simplify RFC 2047 encoding to match Google's own sample
waleedlatif1 Mar 11, 2026
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20 changes: 18 additions & 2 deletions apps/sim/tools/gmail/utils.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -294,6 +294,22 @@ function generateBoundary(): string {
return `----=_Part_${Date.now()}_${Math.random().toString(36).substring(2, 15)}`
}

/**
* Encode a header value using RFC 2047 Base64 encoding if it contains non-ASCII characters.
* Email headers per RFC 2822 must be ASCII-only. Non-ASCII characters (emojis, accented
* characters, etc.) must be encoded as =?UTF-8?B?<base64>?= to avoid mojibake.
* @param value The header value to encode
* @returns The encoded header value, or the original if it's already ASCII
*/
export function encodeRfc2047(value: string): string {
// eslint-disable-next-line no-control-regex
if (/^[\x00-\x7F]*$/.test(value)) {
return value
}
const encoded = Buffer.from(value, 'utf-8').toString('base64')
return `=?UTF-8?B?${encoded}?=`
}
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/**
* Encode string or buffer to base64url format (URL-safe base64)
* Gmail API requires base64url encoding for the raw message field
Expand Down Expand Up @@ -333,7 +349,7 @@ export function buildSimpleEmailMessage(params: {
emailHeaders.push(`Bcc: ${bcc}`)
}

emailHeaders.push(`Subject: ${subject || ''}`)
emailHeaders.push(`Subject: ${encodeRfc2047(subject || '')}`)

if (inReplyTo) {
emailHeaders.push(`In-Reply-To: ${inReplyTo}`)
Expand Down Expand Up @@ -380,7 +396,7 @@ export function buildMimeMessage(params: BuildMimeMessageParams): string {
if (bcc) {
messageParts.push(`Bcc: ${bcc}`)
}
messageParts.push(`Subject: ${subject || ''}`)
messageParts.push(`Subject: ${encodeRfc2047(subject || '')}`)

if (inReplyTo) {
messageParts.push(`In-Reply-To: ${inReplyTo}`)
Expand Down
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