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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘eMail’ Category

Common SMTP message size limits

Posted by jpluimers on 2020/04/08

After a 2018 discussion with a “zorgkantoor” (Dutch for office that arranges for special long term health care needs, successor of AWBZ) about their very low (10 megabyte) SMTP message size limit – even though they expect scanned PDF documents.

Their web-care team posed this limit as normal, so I made a list of limits in their peer group, common world-wide and well-ranked Dutch internet providers.

My plan is to check the progression of these limits over time.

Note these are the bruto message sizes including encoded attachments. Since encoding in [WayBack] MIME Base64 – Wikipedia has a overhead of at least 37% (encoded size is at least 1.37 the original size), the unencoded maximum size is less than 73% of what is listed below.

References:

2018

Read the rest of this entry »

Posted in base64, Communications Development, Development, eMail, Encoding, Internet protocol suite, MIME, Power User, Python, Scripting, SMTP, SocialMedia, Software Development, TCP | Leave a Comment »

mail.com (handled by gmx.com) can reject SMTP connections as early as in the EHLO stage

Posted by jpluimers on 2020/04/06

I found this in one of my logs a a while ago:

Error when executing EHLO command for domain mail.com on SMTP server mx00.mail.com.
(554, 'mail.com (mxgmxus007) Nemesis ESMTP Service not available\nNo SMTP service\nBad DNS PTR resource record.\nFor explanation visit http://postmaster.gmx.com/en/error-messages?ip=37.153.243.242&c=rdns')

It means that gmx.de / mail.com are among the strictest email handling providers I know. I don’t blame them: EHLO is at the start of an extended SMTP session.

At [WayBack] Error messages | GMX Postmaster it indicates:

5xy Bad DNS PTR resource record

Emails from your email server were rejected because the PTR Resource Record (PTR-RR) of your IP address does not follow our guidelines. Possible reasons for this can be:

–jeroen

Posted in Communications Development, Development, eMail, Internet protocol suite, Power User, SMTP, SocialMedia, TCP | Leave a Comment »