all-in-one privacy solution":["Proton Unlimited es una solución de privacidad todo en uno"],"Black Friday":["Black Friday"],"No ads. Privacy by default.":["Sin anuncios. Privacidad por defecto."],"People before profits":["Primero las personas, luego los beneficios"],"Security through transparency":["Seguridad con transparencia"],"The best Proton Mail ${ BLACK_FRIDAY } deals":["Las mejores ofertas de Proton Mail en el ${ BLACK_FRIDAY }"],"The world’s only community- supported email service":["El único servicio de correo electrónico del mundo financiado por la comunidad"]},"specialoffer:limited":{"${ hours } hour":["${ hours } hora","${ hours } horas"],"${ hoursLeft }, ${ minutesLeft } and ${ secondsLeft } left":["Tiempo restante: ${ hoursLeft }, ${ minutesLeft } y ${ secondsLeft }"],"${ minutes } minute":["${ minutes } minuto","${ minutes } minutos"],"${ seconds } second":["${ seconds } segundo","${ seconds } segundos"],"Limited time offer":["Oferta por tiempo limitado"]},"specialoffer:listitem":{"Create multiple addresses":["Cree múltiples direcciones"],"Hide-my-email aliases":["Seudónimos de hide-my-email"],"Quickly unsubscribe from newsletters":["Cancele suscripciones a boletines rápidamente"],"Use your own domain name":["Use su propio dominio"]},"specialoffer:logos":{"As featured in":["Tal como aparece en"]},"specialoffer:metadescription":{"Get an encrypted email that protects your privacy":["Obtenga un correo electrónico cifrado que protege su privacidad"]},"specialoffer:metatitle":{"Proton Mail Black Friday Sale - Up to 40% off":["Oferta de Black Friday de Proton Mail: hasta un 40% de descuento"]},"specialoffer:newmetadescription":{"Get up to 40% off Proton Mail subscriptions this Black Friday. Find great deals on our secure end-to-end encrypted email plans.":["Aproveche las rebajas de Black Friday y obtenga suscripciones de Proton Mail con hasta un 40 % de descuento. Encontrará las mejores ofertas en planes de correo electrónico seguro cifrado de extremo a extremo."]},"specialoffer:newmetatitle":{"Proton Mail Black Friday sale | Up to 40% off secure email":["Rebajas de Black Friday en Proton Mail | Hasta un 40 % de descuento en correo electrónico seguro"]},"specialoffer:note":{"* Billed at ${ TOTAL_SUM } for the first year":["*Con un costo de ${ TOTAL_SUM } durante el primer año"],"*Billed at ${ TOTAL_SUM } for the first 2 years":["*Con un costo de ${ TOTAL_SUM } durante los primeros 2 años"],"30-day money-back guarantee":["Garantía de devolución de dinero de 30 días"],"Billed at ${ TOTAL_SUM } for the first 2 years":["Con un costo de ${ TOTAL_SUM } durante los primeros 2 años"],"Billed at ${ TOTAL_SUM } for the first year":["Con un costo de ${ TOTAL_SUM } durante el primer año"],"You save ${ SAVE_SUM }":["Ahorre ${ SAVE_SUM }"]},"specialoffer:off":{"${ PERCENT_OFF } off":["-${ PERCENT_OFF }"]},"specialoffer:testimonial":{"I love my ProtonMail":["Amo mi Proton Mail"],"My favorite email service":["Mi servicio de correo electrónico favorito"],"Thanks Proton for keeping us all safe in the complicated internet universe.":["Gracias Proton por mantenernos a salvo en el complicado universo de Internet."],"You get what you pay for. In the case of big tech, if you pay nothing, you get used. I quit using Gmail and switched to @ProtonMail":["Obtiene aquello por lo que paga. En el caso de la gran tecnología, cuando uno no paga nada, se acostumbra. Dejé de usar Gmail y cambié a @ProtonMail"]},"specialoffer:time":{"Days":["Días"],"Hours":["Horas"],"Min":["min"]},"specialoffer:title":{"And much more":["Y mucho más"],"Safe from trackers":["A salvo de rastreadores"],"Stay organized":["Mantenga todo en orden"],"Black Friday email deals":["Ofertas en correo electrónico del Black Friday"],"Don’t just take our word for it":["No confíe solo en nuestra palabra"],"Make your inbox yours":["Tome posesión de su bandeja de entrada"],"Our story":["Nuestra historia"],"Transfer your data from Google in one click":["Transfiera sus datos de Google con un solo clic"]},"specialoffer:tooltip":{"Access blocked content and browse privately. Includes ${ TOTAL_VPN_SERVERS }+ servers in ${ TOTAL_VPN_COUNTRIES }+ countries, connect up to 10 devices, access worldwide streaming services, malware and ad-blocker, and more.":["Acceda a contenidos bloqueados y navegue de forma privada. Incluye más de ${ TOTAL_VPN_SERVERS } servidores en más de ${ TOTAL_VPN_COUNTRIES } países, se conecta con hasta 10 dispositivos, accede a servicios de transmisión de todo el mundo, bloquea malware y publicidad y mucho más."],"Easily share your calendar with your family, friends or colleagues, and view external calendars.":["Comparta su calendario con familiares, amigos y compañeros fácilmente y consulte calendarios externos."],"Includes support for 1 custom email domain, 10 email addresses, 10 hide-my-email aliases, calendar sharing, and more.":["Incluye compatibilidad con 1 dominio de correo electrónico personalizado, 10 direcciones de correo electrónico, 10 seudónimos de hide-my-email, posibilidad de compartir calendario, etc."],"Includes support for 3 custom email domains, 15 email addresses, unlimited hide-my-email aliases, calendar sharing, and more.":["Incluye compatibilidad con 3 dominios de correo electrónico personalizado, 15 direcciones de correo electrónico, seudónimos ilimitados de hide-my-email, posibilidad de compartir calendario, etc."],"Manage up to 25 calendars, mobile apps, secured with end-to-end encryption, 1-click calendar import from Google, and more.":["Administre hasta 25 calendarios, apps móviles, protegido con cifrado de extremo a extremo, importación de calendario con 1 clic desde Google y más."]},"Status banner":{"Learn more":["Más información"],"Please note that at the moment we are experiencing issues with the ${ issues[0] } service.":["Tenga en cuenta que, en este momento, estamos experimentando problemas con el servicio ${ issues[0] }."],"We are experiencing issues with one or more services at the moment.":["En este momento, tenemos problemas con uno o más servicios."]},"Status Banner":{"At the moment we are experiencing issues with the Proton VPN service":["En este momento, tenemos problemas con el servicio Proton VPN."],"Learn more":["Más información"]},"steps":{"Step":["Paso"]},"suggestions":{"Suggestions":["Sugerencias"]},"Support":{"Sub category":["Subacategoria","Subcategorías"]},"Support article":{"${ readingTime } min":["${ readingTime } minuto","${ readingTime } minutos"],"Category":["Categoría","Categorías"],"Didn’t find what you were looking for?":["¿No encontró lo que buscaba?"],"General contact":["Contacto general"],"Get help":["Obtener ayuda"],"Legal contact":["Contacto legal"],"Media contact":["Contacto para medios"],"Partnerships contact":["Contacto para colaboradores"],"Reading":["Lectura"]},"Support Form Platform option":{"VPN for Android TV":["VPN para Android TV"],"VPN for Apple TV":["VPN para Apple TV"],"VPN for Chromebook":["VPN para Chromebook"]},"Support troubleshooting":{"App version":["Versión de la app"],"Browser":["Navegador"],"Check if this helps":["Compruebe si le sirve"],"Choose a product":["Elija un producto"],"Did this solve your issue?":["¿Le ha resultado útil para resolver el problema?"],"Faster assistance is just a few clicks away":["Solo le separan unos clics de una asistencia más rápida"],"How can we help?":["¿Cómo podemos ayudarle?"],"No, contact support":["No, contactar a soporte"],"Please fill out one field after another":["Complete un campo después de otro"],"Please make your selections":["Realice sus selecciones"],"Proton account":["Cuenta de Proton"],"Proton for Business":["Proton for Business"],"Thank you for your feedback":["Gracias por sus comentarios"],"What can we help with?":["¿En qué podemos ayudarle?"],"Yes":["Sí"]},"support_modal_search_query":{"Search query":["Consulta"]},"support_search_button":{"Search":["Buscar"]},"support_search_i_am_looking_for":{"I'm looking for":["Busco"]},"SupportForm":{"For a faster resolution, please report the issue from the Bridge app: Help > Report a problem.":["Para una resolución más rápida, reporte el problema desde la app Bridge: Ayuda > Reportar un problema."],"Information":["Información"]},"SupportForm:option":{"Account Security":["Seguridad de la cuenta"],"Contacts":["Contactos"],"Custom email domain":["Dominio de correo electrónico personalizado"],"Email delivery and Spam":["Entrega de correo electrónico y spam"],"Encryption":["Cifrado"],"Login and password":["Inicio de sesión y contraseña"],"Merge aliases and accounts":["Combinar alias y cuentas"],"Migrate to Proton":["Migrar a Proton"],"Notifications":["Notificaciones"],"Other":["Otros"],"Plans and billing":["Planes y facturación"],"Proton for Business":["Proton for Business"],"Sign up":["Regístrese"],"Storage":["Almacenamiento"],"Users, addresses, and identities":["Usuarios, direcciones e identidades"]},"SupportForm:optionIntro":{"Select a topic":["Seleccione un tema"]},"Testimonial":{"Awards":["Premios"],"Customers":["Clientes"],"Featured":["Destacados"],"Go to testimonial source":["Ir a la fuente testimonial"],"Open source of award":["Abrir fuente del premio"],"Open source of quote":["Abrir fuente de la cita"],"Reviews":["Reseñas"],"Videos":["Videos"],"Watch on TikTok":["Ver en TikTok"],"Watch on YouTube":["Ver en YouTube"]},"TestimonialCategory":{"Awards":["Premios"],"Customers":["Clientes"],"Featured":["Destacados"],"Media":["Medios"],"Reviews":["Reseñas"],"Videos":["Videos"]},"Text":{"If you need help, check out our ${ supportLink }.":["Si necesita ayuda, consulte nuestra ${ supportLink }."],"The page you’re looking for might have been removed, or it could be an\nold link.":["Es posible que la página que busca haya sido eliminada o que sea un\nenlace antiguo."],"Your question may already have an answer in our knowledge base:":["Puede que haya respuesta a su pregunta en nuestra base de conocimientos:"]},"Title":{"On this page":["En esta página"],"Related articles":["Artículos relacionados"],"Share ${ thisPage }":["Compartir ${ thisPage }"],"Switch to Proton Pass - Contact us":["Cambie a Proton Pass - Contáctenos"],"Thank you!":["¡Gracias!"],"this page":["esta página"]},"tooltip_vpn":{"Access blocked content and browse privately. Includes ${ TOTAL_VPN_SERVERS }+ servers in ${ TOTAL_VPN_COUNTRIES }+ countries, highest VPN speed, ${ TOTAL_VPN_CONNECTIONS } VPN connections, worldwide streaming services, malware and ad-blocker, and more.":["Acceda a contenidos bloqueados y navegue de forma privada. Incluye más de ${ TOTAL_VPN_SERVERS } servidores en más de ${ TOTAL_VPN_COUNTRIES } países, la mayor velocidad VPN, ${ TOTAL_VPN_CONNECTIONS } conexiones VPN, servicios de transmisión en todo el mundo, bloqueador de malware y publicidad y mucho más."]},"vpn_servers":{"Get Proton VPN Plus":["Obtener Proton VPN Plus"]},"wallet_signup_2024:Action":{"Get Proton Wallet":["Obtener Proton Wallet"]},"wallet_signup_2024:Homepage hero product link title":{"Wallet":["Wallet"]},"wallet_signup_2024:Homepage product navigation bar":{"Wallet":["Wallet"]},"wallet_signup_2024:menu item":{"Bitcoin guide":["Guía sobre Bitcoin"],"Proton Wallet news":["Novedades sobre Proton Wallet"],"Proton Wallet support":["Soporte para Proton Wallet"]},"wallet_signup_2024:Pricing":{"Includes everything in Proton Unlimited and":["Incluye todas las funciones en Proton Unlimited y"],"Limited availability":["Disponibilidad limitada"],"The easiest way to securely own, send, and receive Bitcoin":["La forma más fácil de retener, enviar y recibir Bitcoin con seguridad"]},"wallet_signup_2024:ProductRange":{"Discover Proton Wallet":["Descubra Proton Wallet"],"Store and transact Bitcoin privately with an encrypted self-custody wallet.":["Almacene Bitcoin y negocie de forma privada con una cartera de autocustodia cifrada."]},"wallet_signup_2024:wallet bitcoin":{"Learn about Bitcoin, the Internet's value network.":["Infórmese sobre Bitcoin, la red de valor de internet."]},"wallet_signup_2024:wallet overview":{"Ensure you're always in control of your Bitcoin.":["Asegúrese de tener siempre el control de su Bitcoin."]},"wallet_signup_2024:wallet security":{"The encrypted, open-source wallet that puts you in control.":["La cartera cifrada de código abierto que le permite controlarlo todo."]}}},"base":"support","cdn":{"enabledForAssets":true,"enabledForImages":false,"url":"https://pmecdn.protonweb.com/"},"unleashApi":"https://account.proton.me/api"};
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SMTP (Simple Mail Transfer Protocol) is a standard internet protocol that mail servers use to send and receive emails. If a mail server can’t send an email, it replies with an SMTP error message.
SMTP error messages are messages mail servers send if an incoming or outgoing message bounces. They provide valuable information about why the message wasn’t delivered successfully.
Reviewing the SMTP error code in the bounce message can help you diagnose and resolve the issue.
What do SMTP error messages look like?
SMTP error messages are generally made up of three parts:
1. Reply code
2. Status code
3. Description
xyz Example: 550
x.y.z Example: 5.1.1
Example: “The email account that you tried to reach does not exist.”
Each digit (x, y, and z) in the reply and status codes indicates extra detail about the error.
Here’s an example of an SMTP error message:
SMTP reply codes refer to different aspects of the email service and can indicate issues such as:
The intended recipient’s email address is not registered with the service.
The message has been marked as spam or flagged for containing a virus.
The sender’s domain has been identified as a source of spam.
The email message violates the company’s email policy, such as containing sensitive information like credit card numbers or using prohibited language.
Not all SMTP reply codes indicate errors. Reply codes starting with a “4” or “5” are errors.
Types of SMTP error codes
Errors in SMTP are categorized into two main groups based on the starting digit of the reply code:
Error codes starting with a “4” indicate temporary failures: No immediate action is needed, and the sender’s mail server will automatically retry sending the email.
Error codes starting with a “5” indicate permanent failures: Action is required to resolve the issue and successfully deliver the email.
Understanding and responding to SMTP error codes can help quickly resolve email delivery problems.
For further assistance on email delivery issues, please send us the details of your error using our support form(nueva ventana).
Common SMTP 400 error codes
Error code
SMTP error message
Explanation
421
4.3.0 Temporary System Problem. Try again later.
Temporary issue on the server side; asking the sender to retry later.
421
4.4.5 Server busy, try again later.
The server is currently overloaded; requesting the sender to retry later.
421
4.7.0 IP not in whitelist for RCPT domain, closing connection.
The sending IP address isn’t authorized to send emails to the recipient domain.
421
4.7.0 Our system has detected an unusual rate of unsolicited mail originating from your IP address.
The sending IP address has been blocked temporarily due to suspected spamming.
421
4.7.0 Temporary System Problem. Try again later.
Temporary issue on the server side; asking the sender to retry later.
421
4.7.0 TLS required for RCPT domain, closing connection.
The recipient domain requires TLS encryption for email transmission.
421
4.7.0 Try again later, closing connection. This usually indicates a DoS for the SMTP relay at the HELO stage.
Denial of Service (DoS) attack on the SMTP relay during the initial handshake.
450
4.2.1 The user you are trying to contact is receiving mail too quickly. Please resend your message later.
The recipient’s mailbox is temporarily overloaded; asking the sender to try again later.
450
4.2.1 The user you are trying to contact is receiving mail at a rate that prevents additional messages.
The recipient is receiving emails too quickly, and further messages are delayed.
450
4.2.1 Peak SMTP relay limit exceeded for this customer. This is a temporary error.
The maximum number of SMTP relays has been reached, causing a temporary error.
451
4.3.0 Mail server temporarily rejected message.
Temporary rejection of the message by the recipient’s mail server.
451
4.3.0 Multiple destination domains per transaction are unsupported. Please try again.
Attempt to send emails to multiple domains in a single transaction, which isn’t supported.
451
4.4.2 Timeout – closing connection.
The server closed the connection due to a timeout.
451
4.5.0 SMTP protocol violation, visit RFC 2821.
The SMTP protocol was violated during the exchange of commands.
452
4.2.2 The email account that you tried to reach is over quota.
The recipient’s mailbox is full and cannot accept more messages.
452
4.5.3 Domain policy size per transaction exceeded, please try this recipient in a separate transaction.
The email policy size for the recipient domain has been exceeded.
452
4.5.3 Your message has too many recipients.
The message has too many recipients, and the server can’t process it in a single transaction.
454
4.5.0 SMTP protocol violation, no commands allowed to pipeline after STARTTLS, visit RFC 3207.
A violation of the SMTP protocol occurred after initiating TLS encryption.
454
4.7.0 Cannot authenticate due to temporary system problem. Try again later.
Temporary issue preventing authentication; asking the sender to retry later.
454
5.5.1 STARTTLS may not be repeated.
Attempting to restart TLS encryption when it’s not allowed.
Common SMTP 500 error codes
Error code
SMTP error message
Explanation
501
5.5.2 Cannot Decode response.
The server can’t decode the response from the client.
501
5.5.4 HELO/EHLO argument is invalid.
Invalid argument provided during the HELO/EHLO stage of SMTP.
502
5.5.1 Too many unrecognized commands, goodbye.
The server received too many unrecognized commands and terminates the connection.
502
5.5.1 Unimplemented command.
The server received an unimplemented command and terminates the connection.
502
5.5.1 Unrecognized command.
The server received an unrecognized command and terminates the connection.
503
5.5.1 EHLO/HELO first.
The client should send the EHLO/HELO command first before any other commands.
503
5.5.1 MAIL first.
The client should send the MAIL command before the RCPT command.
503
5.5.1 RCPT first.
The client should send the RCPT command after the MAIL command.
503
5.7.0 No identity changes permitted.
The server doesn’t allow changes to the message sender identity.
504
5.7.4 Unrecognized Authentication Type.
The server doesn’t recognize the authentication type used by the client.
530
5.5.1 Authentication Required.
Authentication is required to send emails through the server.
530
5.7.0 Must issue a STARTTLS command first.
The client must issue the STARTTLS command before attempting to authenticate.
535
5.5.4 Optional Argument not permitted for that AUTH mode.
An optional argument isn’t allowed for the specified authentication mode.
535
5.7.1 Application-specific password required.
An application-specific password is required for authentication.
535
5.7.1 Please log in with your web browser and then try again.
The user must log in through the web browser to resolve authentication issues.
535
5.7.1 Username and Password not accepted.
The provided username and password aren’t accepted for authentication.
550
5.1.1 The email account that you tried to reach does not exist.
The recipient’s email address doesn’t exist or is misspelled.
550
5.2.1 The email account that you tried to reach is disabled.
The recipient’s email account is disabled and can’t receive messages.
550
5.2.1 The user you are trying to contact is receiving mail at a rate that prevents additional messages.
The recipient is receiving emails too quickly, and further messages are delayed.
550
5.4.5 Daily sending quota exceeded.
The sender has exceeded their daily email sending quota.
550
5.4.5 Daily SMTP relay limit exceeded for user.
The sender has exceeded their daily SMTP relay limit.
550
5.7.0 Mail relay denied.
The server has denied mail relay for the sender’s IP address.
550
5.7.1 Email quota exceeded.
The recipient’s email account has exceeded its quota and can’t receive more messages.
550
5.7.1 Invalid credentials for relay.
The provided credentials for SMTP relay are invalid.
550
5.7.1 Our system has detected an unusual rate of unsolicited mail from your IP address.
The sender’s IP address has been blocked due to suspected spamming.
550
5.7.1 Our system has detected that this message is likely unsolicited mail.
The message has been blocked as it appears to be spam.
550
5.7.1 The IP you’re using to send mail is not authorized to send email directly to our servers.
The sender’s IP isn’t authorized to send emails directly to the recipient’s server.
550
5.7.1 The user or domain you are sending to (or from) has a policy that prohibited the mail that you sent.
The recipient domain has a policy that blocked the sent email.
550
5.7.1 Unauthenticated email is not accepted from this domain.
The server doesn’t accept unauthenticated emails from the specified domain.
550
5.7.1 Daily SMTP relay limit exceeded for customer.
The sender has exceeded their daily SMTP relay limit.
550
5.7.26 Unauthenticated email from domain-name is not accepted due to the domain’s DMARC policy.
The domain’s DMARC policy is blocking unauthenticated emails.
552
5.2.2 The email account that you tried to reach is over quota.
The recipient’s mailbox is full and can’t accept more messages.
552
5.2.3 Your message exceeded Google’s message size limits.
The message size exceeds the maximum allowed by Google’s email service.
553
5.1.2 We weren’t able to find the recipient domain.
The recipient domain doesn’t exist or has a typo in the email address.
554
5.6.0 Mail message is malformed. Not accepted.
The email message is malformed and can’t be accepted.
554
5.6.0 Message exceeded 50 hops, this may indicate a mail loop.
The message has passed through too many servers, suggesting a mail loop.
554
5.7.0 Too Many Unauthenticated commands.
The server received too many unauthenticated commands and terminates the connection.
555
5.5.2 Syntax error.
The server encountered a syntax error in the client’s command.