content-type email

sSMTPedia

Try SMTPing

Email Verification
Featured Guides
Key Topics
Free Tool
SMTPing
25 free checks daily
13 validation types, no card required.
Try free →
Email Settings
Popular Providers
Configuration Topics
Free Tool
SMTPing
25 free checks daily
13 validation types, no card required.
Try free →
Marketing Platforms
Platforms
Mailchimp
Mailchimp review
Mailchimp pricing
Mailchimp alternatives
Mailchimp SMTP settings
Mailchimp integrations
Mailchimp API + MCP
Constant Contact
Constant Contact pricing
Constant Contact SMTP settings
Constant Contact integrations
Constant Contact API + MCP
Klaviyo
Klaviyo pricing
Klaviyo SMTP settings
Klaviyo integrations
Klaviyo API + MCP
SendGrid
SendGrid pricing
SendGrid SMTP settings
SendGrid integrations
SendGrid API + MCP
MailerLite
MailerLite pricing
MailerLite SMTP settings
MailerLite integrations
MailerLite API + MCP
ActiveCampaign
ActiveCampaign pricing
ActiveCampaign SMTP settings
ActiveCampaign integrations
ActiveCampaign API + MCP
Brevo
Brevo pricing
Brevo SMTP settings
Brevo integrations
Brevo API + MCP
Amazon SES
Amazon SES pricing
Amazon SES SMTP settings
Amazon SES integrations
Amazon SES API + MCP
Tool Roundups
Free Tool
SMTPing
25 free checks daily
13 validation types, no card required.
Try free →
Deliverability
Essential Guides
Topics
Free Tool
SMTPing
25 free checks daily
13 validation types, no card required.
Try free →
Standards & Protocols
Authentication & DNS
Codes, RFCs & MTAs
Free Tool
SMTPing
25 free checks daily
13 validation types, no card required.
Try free →
Top Picks
Editor’s Selection · the highest-leverage reads on SMTPedia
Must-Read Pillars
Best Of 2026
Free Tool
SMTPing
25 free checks daily
13 validation types, no card required.
Try free →
Free Tools
Generators
Checkers
Premium Tool
SMTPing
25 free checks daily
Email verification with 13 validation types.
Try free →
Downloads
Courses

SMTPedia

The Email Wiki

content-type email

Headers & MIME

Content-Type and MIME Structure in Email: Multipart, Encodings and Boundaries (RFC 2045-2049)

Alaa 28 August 2026

Content-Type and MIME structure in email: the RFC 2045-2049 rules for multipart/alternative, multipart/mixed, multipart/related, and their nesting. Covers boundaries, character sets, the four ...