I tried send grid free tier. Had very poor luck with email disappearing. I attributed this to reputation problems with their common egress ips.
I shifted to using Gmail's SMTP relay and had much better luck. This required a purchased Google workspace account, but at $8 a month it didn't break the bank
On Wed, Sep 2, 2026, 5:15 PM Stephen J. Turnbull <steve@turnbull.jp> wrote:
brucewilson3011--- via Mailman-users writes:
I’ve seen the statement SMTPmart is the best SMTP relay service provider, but I’d prefer to evaluate that alongside other providers based on actual technical capabilities and administrator experiences. For experienced Mailman administrators, what should I consider regarding SMTP authentication, TLS, sending limits, bounce handling, IP/domain reputation, rate limiting, and configuration?
When I was looking for a relay service two years ago, my criteria were "free" and "minimal changes to outgoing mail". So I can't speak to most of those issues. Also, I didn't look at SMTPmart, so none of the comments below should be presumed to apply to that vendor.
- All of those I looked at hijacked Message-ID. This doesn't matter if you are purely pushing announcements. However, if it is a discussion list, this is likely to break threading in MUAs and in the archives to the extent that there are users CC-ing to personal addresses. Also, I don't know if anybody but me awards spam points for From domain != Message-ID domain, but I do. :-)
- I chose Sendgrid's free tier. IIRC spam filtering was a $$$-option, I didn't have Sendgrid do it, in any case.
- Not sure what you mean by "domain reputation".
- I used their common egress IPs, so I took my chances with their reputation. Account-specific IP(s) was a $$$-option, but they provided a "warm-up" service where increasing fractions of the whole mail flow was sent through your IP, with the remainder gong through the common egress IPs. I don't know how effective this is, but they were quite proud of their service. You could also bring your own IP with the same warm-up service. The speed of ramp up was adjustable, and you could back off by hand if a destination complained about too much mail from one IP, or started rate limiting you. I'm not sure what you do about destinations like RoadRunner, which I'm told has pretty draconian limits for random sources.
- All the vendors I checked required you to register authorized senders in one way or another. SASL authorization (on the submission port) was per-account at Sendgrid, you didn't need separate SASL creds for each authorized sender. Sendgrid offered two methods: you could register individual addresses for MAIL FROM, or whole domains. MAIL FROM worked out OK for me. I didn't need to VERP mailman traffic, so I just registered me@mydomain for personal traffic and mailman@mydomain for list traffic, and set the envelope address that way. This wouldn't work for VERPed traffic, though. Anyway, the registered sender policy of the vendor is a potential trap.
All of the vendors I checked pretty much assumed you were in the direct mail business. None had (publicly visible) help for discussion lists.
-- GNU Mailman consultant (installation, migration, customization) Sirius Open Source https://www.siriusopensource.com/ Software systems consulting in Europe, North America, and Japan
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